Week 15 · Chapter

Chapter 15 — Population, Urbanization & Social Change

Introduction to Sociology Free sample edition

The module's primary reading · ~40–50 minutes · Objective 8 (analyze social change — demography and the demographic transition, urbanization, collective behavior, and social movements and their theories — and the forces that drive it, reading population data for what a rate measures), building on Objective 1 (apply the sociological imagination — connecting personal troubles to public issues — and the three major theoretical perspectives (structural functionalism, conflict theory, symbolic interactionism) to interpret a social phenomenon, naming the level of analysis each works at and placing the discipline's founders with the ideas and works they are known for) and Objective 2 (describe and evaluate the major sociological research methods (surveys, experiments, field research and ethnography, secondary-data analysis), distinguish reliability from validity and a population from a sample, and read a social statistic critically — what it measures, over what population and period, what it shows and does not, and whether it is a correlation or a cause) · Read it first this week; the lecture, the slide deck, the tutorial, the quiz, and the Sociology in Action Workshop all build on it.

In plain language

Every society is always changing: people are born, people die, people move, cities spread, and groups organize to push for something new. This week you study those changes. You will learn demography (the study of how populations grow, shrink, and move) and read a real figure on how many children women around the world have. You will see how cities grow and what city life does to relationships. Then you will tell a passing crowd from a social movement (an organized, lasting effort to bring about or resist change), sort movements by what they want, and ask why some of them rise and last.

Why you already care about this

In Our World in Data's presentation of the United Nations World Population Prospects, the world's total fertility rate was 2.3 children per woman in 2023. In the 1950s it was 4.9. That is a fall of more than half in about seven decades, and it touches nearly every country on earth.

You have lived the edges of this change. Maybe your grandparents grew up with five or six siblings and you have one or none. Maybe your family moved to a new city for a job, or a cousin moved away for school and never came back. Maybe a new apartment tower or a new rail line went up in your neighborhood, and the corner store changed hands. Maybe you signed a petition, joined a walkout, or watched a crowd gather on the news and wondered whether it would turn into something more.

Each of those moments is a small piece of a large pattern. This last chapter of the course gives you the tools to read that pattern: how populations change, how cities grow, how people organize, and how a whole society shifts over time.

By the end of this chapter you will be able to:

define demography's three drivers and compute a crude birth rate, a crude death rate, and natural increase from counts;
explain the total fertility rate as a rate built from age-specific birth rates, and show why a falling rate can still come with more births;
walk the four stages of the demographic transition as a model, and keep Malthus's argument separate from it;
describe the concentric-zone model and Wirth's urbanism, and name suburbanization;
sort an event as collective behavior or a social movement, and sort a movement into one of Aberle's four types;
match a movement's story to relative deprivation, resource mobilization, political process, framing, or new social movement theory;
run one change through structural functionalism, conflict theory, and symbolic interactionism, naming each level;
read the 2023 and 1950s fertility figures four ways, with the arithmetic shown.

Carry this line with you: a rate is not a count — read the base first.

Where we are

Already covered: Week 1 gave you the sociological imagination, the three perspectives, and rates per 100,000. Week 2 taught the four data questions and the percentage point. Week 3 named cultural lag. Week 9 read the world's countries and their inequality. Week 13 met Weber's Protestant ethic, and Week 14 read power, authority, and the state.
This week: how populations grow and move, how the demographic transition models that growth, how cities form and what they do to daily life, how crowds differ from movements, how movements are sorted and explained, and what drives social change.
How they connect: Week 1's rates return as birth and death rates per 1,000; Week 14's question of who holds power returns as the question of how ordinary people organize to change it.

This is the final module of the course, so it also looks back. Week 1 is the chapter this one leans on most. There you learned that a rate is a count divided by a population, with the base written out, so places of different sizes can be compared. This week you use rates per 1,000 people and per 1,000 women. Week 2's four questions return in Section 9: what is measured, over whom and when, what it shows and does not, and whether it is a correlation or a cause. After this module comes the finals week, with the Final Practice Exam and the final, and no new material.

1. Count the people: births, deaths, and moves

Picture an illustrative town council at a meeting. One council member wants a new elementary school. Another wants a new senior center. Both are making a guess about the town's future population. A sociologist would ask them to look at three numbers first: births, deaths, and moves.

Demography is the scientific study of human populations: their size, their makeup, and how they change through births, deaths, and moves.

A population changes in only three ways, and you can name each one.

Fertility is childbearing in a population, measured by how many births occur and to whom.
Mortality is death in a population, measured by how many deaths occur and at what ages.
Migration is the movement of people into or out of a place, whether across a border or within one country.

Counts of births and deaths are hard to compare across places of different sizes, so demographers turn them into rates, the move you learned in Week 1.

The crude birth rate is the number of live births in a year for every 1,000 people in a population.
The crude death rate is the number of deaths in a year for every 1,000 people in a population.
Natural increase is the crude birth rate minus the crude death rate: the growth a population gets from births and deaths alone, before anyone moves in or out.

Worked example — one illustrative town's year. An illustrative town of 50,000 people records 600 births and 450 deaths in one year.

Crude birth rate. 600 ÷ 50,000 × 1,000 = 12 births per 1,000 people.
Crude death rate. 450 ÷ 50,000 × 1,000 = 9 deaths per 1,000 people.
Natural increase. 12 − 9 = 3 per 1,000 people a year.

In words: for every 1,000 residents, births added 12 people and deaths removed 9, so the town grew by 3 per 1,000 before counting anyone who moved. The council would still need the migration numbers before choosing between the school and the senior center.

Now follow the movers. Every move has reasons, and you can sort them into two kinds.

A push factor is a condition that drives people to leave a place, such as a closed workplace, a drought, or danger.
A pull factor is a condition that draws people to a place, such as job openings, relatives who can help, or safety.

Worked example — one illustrative move. A family leaves a coastal town after the fish-packing plant closes and settles in an inland city where a hospital is hiring.

Push. The plant closing drives the family out of the coastal town.
Pull. The hospital jobs draw the family to the inland city.

In words: the same move had a reason to leave and a reason to arrive. Most moves have both, so you name each one.

Misconception check — "the town with more births is growing faster." Students often compare two towns by their number of births. It is tempting, because a bigger number looks like more growth. But a town of 200,000 with 1,600 births has a crude birth rate of 1,600 ÷ 200,000 × 1,000 = 8 per 1,000, lower than the illustrative town's 12. The cure is Week 1's rule: compare rates, and name the base.

Memory hook: births, deaths, moves — and always per 1,000.

2. Read fertility as a rate: the total fertility rate and momentum

Ask a friend how many children people "have these days," and you will get a guess based on the families they know. Demographers need something better: one number that sums up a year's childbearing for a whole population. That number is a rate, and it is easy to misread.

Start with the building block.

An age-specific birth rate is the number of births in a year to women in one age group, for every 1,000 women in that age group.

Women of different ages have children at very different rates, so demographers measure each age group separately and then combine them.

The total fertility rate is the average number of children a woman would have if she lived through her childbearing years at the current age-specific birth rates; it is a synthetic measure, not a count of any real woman's children.
Children per woman is the unit of the total fertility rate: a synthetic average for one woman at current rates, not a count of any real woman's children.

Worked example — building a rate, illustrative. In an illustrative country, the age-specific birth rates for seven five-year age groups, ages 15 to 49, are 20, 90, 120, 100, 50, 15, and 5 births per 1,000 women a year.

Add the rates. 20 + 90 + 120 + 100 + 50 + 15 + 5 = 400 births per 1,000 women for one year of each age group.
Five years in each group. A woman spends five years in each age group, so 400 × 5 = 2,000 births per 1,000 women across the childbearing years.
Per woman. 2,000 ÷ 1,000 = 2.0 children per woman.

In words: if a woman lived through every age group at this year's rates, she would have 2.0 children on average. No real woman lived through those seven age groups this year. The rate imagines one woman living through today's rates, which is why it is synthetic.

Now the surprising part. A falling birth rate does not mean fewer births right away.

Population momentum is the tendency of a population to keep growing for decades after its fertility falls, because a large young generation is entering its childbearing years.

Worked example — momentum, illustrative. In an illustrative country, you compare two years.

The first year. 100,000 women are in their childbearing years, and the rate is 100 births per 1,000 women, so 100,000 × 100 ÷ 1,000 = 10,000 births.
Twenty years later. 150,000 women are in their childbearing years, and the rate has fallen to 80 births per 1,000 women, so 150,000 × 80 ÷ 1,000 = 12,000 births.
The difference. 12,000 − 10,000 = 2,000 more births at a lower rate.

In words: the rate fell, yet births rose, because far more women were of childbearing age. A school district in that country would still need more kindergarten seats, even though each woman was having fewer children. Honesty note: these numbers are illustrative, built for this course to show the idea, and they describe no real country.

Misconception check — "the total fertility rate is the average family size today." Students often read 2.0 children per woman as the size of today's families. It is tempting, because the unit says "children per woman." But the rate is built from this year's age-specific rates and describes an imagined woman, not any real family. The cure: say "at current rates," every time.

Misconception check — "a falling birth rate means a falling population." Momentum is the cure. A large young generation can keep births above deaths for decades, so read the rate and the count separately.

Memory hook: a rate is not a count — read the base first.

3. Walk the demographic transition: a model, and Malthus beside it

Picture the same illustrative country across two centuries. At first, many babies are born and many people die young. Then fewer people die young, while births stay high. Later, families start having fewer children. Finally, births and deaths both settle low. Sociologists hold that story in one hand as a model.

The demographic transition is a classroom model of a staged path from high birth and death rates, through falling death rates and then falling birth rates, to low and stable rates of both.

You treat it as a model, not a law that every country follows on a fixed schedule. It describes a pattern that industrial societies went through.

Worked example — the transition, illustrative. In an illustrative country, the birth and death rates in each stage, per 1,000 people a year, are set out below.

Illustrative birth rates, death rates, and natural increase per 1,000 people a year in the four stages of the demographic transition, constructed for this course
Stage	Births per 1,000	Deaths per 1,000	Natural increase per 1,000
Stage 1: both high	40	38	2
Stage 2: deaths fall	40	20	20
Stage 3: births fall	25	12	13
Stage 4: both low	12	11	1

Stage 1. 40 − 38 = 2 per 1,000 people a year.
Stage 2. 40 − 20 = 20 per 1,000 people a year.
Stage 3. 25 − 12 = 13 per 1,000 people a year.
Stage 4. 12 − 11 = 1 per 1,000 people a year.

In words: growth is fastest in stage 2, when deaths have fallen and births have not. Stage 2's natural increase of 20 versus stage 4's 1 is a growth rate 20 times as fast. A government in stage 2 has to plan for many more schools; a government in stage 4 plans for an older population.

Malthus offered a darker argument about population. Malthus (1798), An Essay on the Principle of Population, argued that population tends to outrun food. When it does, he wrote, positive checks bring it back down.

Positive checks are, in Malthus's argument, the famine, disease, and war that raise death rates when population outruns food, restoring the balance.

Misconception check — Malthus and the transition swapped. Students often say Malthus described the demographic transition. It is tempting, because both are about population and food and growth. But Malthus predicted the checks; the transition describes what industrial societies did, as their birth rates fell. The cure: Malthus is a prediction of checks, and the transition is a model of stages.

Caveat: neither idea is a verdict about any one country today. You read each as an argument from its own time (Malthus) or a model (the transition), and you test both against data.

Memory hook: Malthus predicted checks; the transition describes stages.

4. Watch the city grow: urbanization and the Chicago School

Think about the last time you rode a crowded bus or train. You were close to dozens of people and knew none of them. You paid a driver whose name you did not know. You bought coffee from someone you will never see outside the shop. That is a city way of life, and sociologists set out to explain it.

Urbanization is the growth in the share of a population that lives in cities.
The Chicago School is the early twentieth-century group of sociologists who studied the city as a kind of ecology, including Burgess's concentric-zone model and Wirth's account of urbanism.

Burgess (1925), "The Growth of the City", offered a picture of how a city spreads.

The concentric-zone model is Burgess's classroom model of a growing city spreading outward in rings from the central business district.

Wirth (1938), "Urbanism as a Way of Life", asked what city life does to people.

Urbanism is the way of life that Wirth linked to a city's size, density, and diversity, marked by impersonal and segmented relationships.

"Segmented" means you know most people through one slice of their lives: the bus driver as a driver, the barista as a barista.

As cities grow, many people move to their edges.

Suburbanization is the growth of communities at the edge of a city, where more people live and from which many travel into the center.

Worked example — testing the rings, illustrative. An illustrative river city has its oldest blocks downtown, with newer neighborhoods spreading outward and a ring of suburbs at the edge. But one long strip of factories follows the river straight out of town, and a wealthy hillside sits close to the center.

Where the model fits. The city spreads outward from its central business district, and the newest homes sit farthest out, in the suburbs.
Where the model fails. The river strip and the hillside break the rings.
What you conclude. The concentric-zone model describes part of this city's growth and misses the rest, which is what a model is for.

In words: a model is a simplification you can hold in one hand. You test it against the city you know.

Misconception check — "every city is a set of rings." Students often treat the concentric-zone model as a map of real cities. It is tempting, because the picture is neat. But it is a model, and few real cities draw perfect rings. The cure: say "Burgess's model predicts," then check the real city.

Limitation: this course pins no world urban share. Countries define "urban" in different ways, so you read any such figure at its source, with its year and its definition, and you never treat it as a settled fact.

Memory hook: rings are a model; check the river.

5. Tell a crowd from a movement

Imagine two illustrative scenes in one city. In the first, the power fails during a concert, and a crowd of thousands spills into the street, talking, filming, and drifting home within an hour. In the second, a dozen tenants in an old building meet every month for three years to press their landlord for repairs. Which one is changing society? The answer depends on two ideas.

Collective behavior is relatively spontaneous, short-lived action by a large number of people, such as a crowd, a rumor, a fad, or a panic.
A social movement is an organized, sustained effort by many people to bring about or to resist change.

Worked example — sorting four illustrative events. Decide which is collective behavior and which is a social movement.

A rumor of a gas shortage sends hundreds of drivers to the pumps in one afternoon. Spontaneous and short-lived: collective behavior, here a panic.
The tenants' group that meets monthly for three years. Organized and sustained: a social movement, even though it is small.
A dance from an online video that sweeps a campus for two weeks and fades. Spontaneous and short-lived: collective behavior, here a fad.
A neighborhood campaign that holds meetings, keeps a mailing list, and lobbies the city for bike lanes over several years. Organized and sustained: a social movement.

In words: the test is organization and staying power. The crowd of thousands was larger than the tenants' group, and it was still collective behavior.

Misconception check — "a big crowd is a movement." Students often sort by size. It is tempting, because a large crowd looks powerful. But a crowd that disperses in an hour has no organization and no staying power. The cure: ask "is it organized, and does it last?"

Pause and think. Choose one: (a) describe a crowd, fad, or rumor you saw spread, in person or online, and say why it stayed collective behavior; or (b) describe a group you know of that meets again and again to change something, and say what keeps it organized.

Memory hook: organized and lasting, not big and loud.

6. Sort movements by aim: Aberle's four types

Some movements want you to change one habit. Others want to remake the whole society. A sociologist sorting movements asks two questions about the aim, never about the size.

Aberle (1966), The Peyote Religion among the Navaho, classified movements by whom they aim to change, individuals or society as a whole, and by how much, partly or totally. Two questions with two answers each give four types.

Aberle's four types of social movement, sorted by whom a movement aims to change and how much
How much change	Change in individuals	Change in society
Partial change	Alterative	Reformative
Total change	Redemptive	Transformative

An alterative movement is, in Aberle's model, a movement that seeks a partial change in individuals; alterative is Aberle's term, and courses often render it as alternative.
A redemptive movement is, in Aberle's model, a movement that seeks a total change in individuals.
A reformative movement is, in Aberle's model, a movement that seeks a partial change in society.
A transformative movement is, in Aberle's model, a movement that seeks a total change in society, often taught as a revolutionary movement.

Worked example — sorting four illustrative movements. Ask "whom?" and then "how much?"

A campaign asking people to put their phones away during family meals. Whom: individuals. How much: one habit. Alterative.
A fellowship that asks each new member to leave an old way of life completely and start a new one. Whom: individuals. How much: totally. Redemptive.
The bike-lane campaign from Section 5, asking the city to change one law. Whom: society, through its rules. How much: partly. Reformative.
A movement that seeks to replace a country's whole system of government and ownership. Whom: society. How much: totally. Transformative.

In words: the type comes from the aim. A tiny group can be transformative, and a huge one can be alterative.

Misconception check — "the biggest movements are the transformative ones." Students often classify a movement by how many people join it. It is tempting, because large movements feel revolutionary. But Aberle's model asks whom a movement seeks to change and how much, and size is not one of its questions. The cure: answer "whom?" and "how much?" before you name a type.

Memory hook: whom, then how much — never how many.

7. Ask why movements rise and how they age

Return to the illustrative tenants' group. Why did these tenants organize, when the tenants next door did not? Why did their campaign last three years when many others fade in a month? You will find that sociologists offer several answers. Each one points at a different part of the story, and you weigh them side by side.

Relative deprivation theory is the theory that people organize into movements when they feel deprived compared with what they expected or with what others have.
Resource mobilization theory is the theory, from McCarthy and Zald (1977), "Resource Mobilization and Social Movements", that a movement's success depends on the money, time, people, and organization it can marshal.
Political process theory is the theory that a movement's chances rise and fall with openings and closings in the political system around it.
Framing is the way a movement presents an issue so that people see a problem, a solution, and a reason to act, through diagnostic, prognostic, and motivational frames. The idea comes from Snow and Benford (1988). A diagnostic frame names the problem, a prognostic frame offers a solution, and a motivational frame gives people a reason to act.
New social movement theory is the theory that addresses movements in postindustrial societies organized around identity, quality of life, and values rather than around class alone.

Movements also change as they age.

The movement life cycle is a commonly taught model of the stages a social movement passes through: emergence, coalescence, bureaucratization or institutionalization, and decline.

Honesty note: conventions differ on the stage labels, so you learn the idea of stages rather than one fixed list. Decline is not always failure; a movement can fade because it won.

Worked example — the tenants' group, read five ways. You take the theories one at a time and ask what each one helps you see.

Relative deprivation. The tenants compare their broken heaters with the newer building across the street, where repairs come fast.
Resource mobilization. They collect small dues, run a phone tree, and share volunteer hours.
Political process. A new city council member supports building inspections, which opens a door.
Framing. Diagnostic: "The landlord ignores repairs." Prognostic: "A city inspection and a written repair plan." Motivational: "If we act together, every apartment has heat this winter."
Life cycle. The group emerged when the heat failed, coalesced at its first meeting, and moved toward bureaucratization when it elected officers and registered as an association.

In words: each theory explains a different piece. No single theory is declared correct.

Misconception check — "the poorest people always rebel first." Students often read relative deprivation as "the people with the least organize." It is tempting, because hardship seems like enough. But the theory says deprivation is relative: people compare what they have with what they expected or with what others have. The cure: ask "compared with what?"

Memory hook: compared with what, with what resources, through which door, in which frame?

8. Name the engines of change and read them three ways

Think of how your own neighborhood has changed in your lifetime. A store closed, a phone app replaced a habit, a new law changed a rule, a group won a fight. Sociologists call the sum of those shifts by one name.

Social change is the transformation of a society's culture, structure, and institutions over time.

You can name four engines that drive it, and you have met three of them already in this course.

Technology. New tools change how people live, and the norms around them catch up slowly; that gap is the cultural lag Ogburn named, which you met in Week 3.
Conflict. Marx read change as the result of struggle between groups over resources, the conflict tradition you have used all term.
Ideas. Weber's account of the Protestant ethic, from Week 13, argued that a set of ideas can fit with, and strengthen, a new economic spirit.
Social movements. Organized people press for change, as Sections 5 to 7 showed.

Worked example — a new rail station, three lenses. An illustrative neighborhood gets a new rail station. Read the same change through each perspective.

Structural functionalism (macro). The station is a society adjusting its parts: more workers reach jobs downtown, and the city's transit system regains balance after years of crowded roads.
Conflict theory (macro). Land near the station gains value. Owners profit, while renters may face higher rents and be pushed out, so the change sorts winners from losers.
Symbolic interactionism (micro). Residents redefine their neighborhood. A place once called "far from everything" becomes "a quick ride downtown," and the corner where people waited for the bus becomes a new meeting spot with new meanings.

In words: the first two lenses read the station at the macro level of a city's structure, and the third reads it at the micro level of the meanings people share. No lens is declared correct; each answers a different question.

Misconception check — "change has one cause." Students often name a single engine, usually technology, as the driver of all change. It is tempting, because new tools are easy to see. But the station needed money, a political decision, and people who pushed for it, and its effects ran through meanings as well as markets. The cure: name more than one engine, and say which lens you are using.

Pause and think. Choose one: (a) name one change in your own community and say which of the four engines drove it; or (b) name one change and run it through one of the three perspectives, naming that lens's level of analysis.

Memory hook: tools, conflict, ideas, movements — four engines, three lenses.

9. Read the world's fertility figure: four questions, then a look back

Now you read the real figure with Week 2's four questions. The source is Our World in Data's presentation of the United Nations World Population Prospects.

Global total fertility rate in children per woman, the 1950s and 2023, from Our World in Data's presentation of the United Nations World Population Prospects
Period	Global total fertility rate
The 1950s	4.9 children per woman
2023	2.3 children per woman

Worked example — the global total fertility rate, read four ways. Take the steps in order.

What is measured? The total fertility rate, the average number of children a woman would have at the current age-specific birth rates.
Over whom? The world's population of women in their childbearing years, in 2023, compared with the 1950s. The 1950s figure describes a decade, not one year.
What does it show? Work it one step at a time.
- The figures: 2.3 children per woman in 2023, against 4.9 in the 1950s.
- The change in children: 4.9 − 2.3 = 2.6 fewer children per woman.
- The change as a percent: 2.6 ÷ 4.9 × 100 ≈ 53.1, so the rate fell by about 53 percent, more than half, in about seven decades.
- What is left: 2.3 ÷ 4.9 × 100 ≈ 46.9, so the 2023 rate was a little under half the 1950s rate.
What does it not show? The size of any family today, the number of children any real woman had, why the rate fell, or that the world's population is shrinking. Section 2's momentum can keep a population growing after its fertility falls.
Correlation or cause? Neither. You are reading a description of fertility in two periods. The demographic transition describes the fall and does not by itself explain it.

In words: around the world, a woman living through today's rates would have a little more than two children, where in the 1950s she would have had nearly five. The figure describes a change; it does not explain it. A health ministry planning maternity wards and a school board planning classrooms would both start from this kind of rate, then look at the count of women of childbearing age.

In practice (your tools). You can check every step in a free spreadsheet. Type 4.9 in A1 and 2.3 in A2. In A3, type =A1-A2 to get 2.6, the fall in children per woman. In A4, type =A3/A1*100 to get about 53.1, the percent fall. In A5, type =A2/A1*100 to get about 46.9, the share that is left.

Misconception check — "the world's population is shrinking." Students often read a falling fertility rate as a falling population. It is tempting, because fewer children per woman sounds like fewer people. But the rate is not a count, and momentum keeps a population growing while a large young generation has children. The cure: read the rate and the count separately.

Now look back at the whole course. In Week 1 you met Mills's sociological imagination: the habit of reading a private life inside a public pattern. You have used that habit ever since. You ran families, schools, congregations, workplaces, and governments through three lenses, each at its own level. You read rates, shares, medians, and ratios for what they measure and what they do not. This week's fertility figure is the same move one more time: a private decision about children, read as a public pattern across the world.

Memory hook: a private choice, a public rate — the imagination at work.

For more on this week's ideas, the module's Readings & Resources page links to short articles and videos.

Key terms

Demography — The scientific study of human populations: their size, their makeup, and how they change through births, deaths, and moves. (first used: 1. Count the people: births, deaths, and moves)
Fertility — Childbearing in a population, measured by how many births occur and to whom. (first used: 1. Count the people: births, deaths, and moves)
Mortality — Death in a population, measured by how many deaths occur and at what ages. (first used: 1. Count the people: births, deaths, and moves)
Migration — The movement of people into or out of a place, whether across a border or within one country. (first used: 1. Count the people: births, deaths, and moves)
Crude birth rate — The number of live births in a year for every 1,000 people in a population. (first used: 1. Count the people: births, deaths, and moves)
Crude death rate — The number of deaths in a year for every 1,000 people in a population. (first used: 1. Count the people: births, deaths, and moves)
Natural increase — The crude birth rate minus the crude death rate: the growth a population gets from births and deaths alone, before anyone moves in or out. (first used: 1. Count the people: births, deaths, and moves)
Push factor — A condition that drives people to leave a place, such as a closed workplace, a drought, or danger. (first used: 1. Count the people: births, deaths, and moves)
Pull factor — A condition that draws people to a place, such as job openings, relatives who can help, or safety. (first used: 1. Count the people: births, deaths, and moves)
Age-specific birth rate — The number of births in a year to women in one age group, for every 1,000 women in that age group. (first used: 2. Read fertility as a rate: the total fertility rate and momentum)
Total fertility rate — The average number of children a woman would have if she lived through her childbearing years at the current age-specific birth rates; a synthetic measure, not a count of any real woman's children. (first used: 2. Read fertility as a rate: the total fertility rate and momentum)
Children per woman — The unit of the total fertility rate: a synthetic average for one woman at current rates, not a count of any real woman's children. (first used: 2. Read fertility as a rate: the total fertility rate and momentum)
Population momentum — The tendency of a population to keep growing for decades after its fertility falls, because a large young generation is entering its childbearing years. (first used: 2. Read fertility as a rate: the total fertility rate and momentum)
Demographic transition — A classroom model of a staged path from high birth and death rates, through falling death rates and then falling birth rates, to low and stable rates of both. (first used: 3. Walk the demographic transition: a model, and Malthus beside it)
Positive checks — In Malthus's argument, the famine, disease, and war that raise death rates when population outruns food, restoring the balance. (first used: 3. Walk the demographic transition: a model, and Malthus beside it)
Urbanization — The growth in the share of a population that lives in cities. (first used: 4. Watch the city grow: urbanization and the Chicago School)
Chicago School — The early twentieth-century group of sociologists who studied the city as a kind of ecology, including Burgess's concentric-zone model and Wirth's account of urbanism. (first used: 4. Watch the city grow: urbanization and the Chicago School)
Concentric-zone model — Burgess's classroom model of a growing city spreading outward in rings from the central business district. (first used: 4. Watch the city grow: urbanization and the Chicago School)
Urbanism — The way of life that Wirth linked to a city's size, density, and diversity, marked by impersonal and segmented relationships. (first used: 4. Watch the city grow: urbanization and the Chicago School)
Suburbanization — The growth of communities at the edge of a city, where more people live and from which many travel into the center. (first used: 4. Watch the city grow: urbanization and the Chicago School)
Collective behavior — Relatively spontaneous, short-lived action by a large number of people, such as a crowd, a rumor, a fad, or a panic. (first used: 5. Tell a crowd from a movement)
Social movement — An organized, sustained effort by many people to bring about or to resist change. (first used: 5. Tell a crowd from a movement)
Alterative movement — In Aberle's model, a movement that seeks a partial change in individuals; courses often render the term as alternative movement. (first used: 6. Sort movements by aim: Aberle's four types)
Redemptive movement — In Aberle's model, a movement that seeks a total change in individuals. (first used: 6. Sort movements by aim: Aberle's four types)
Reformative movement — In Aberle's model, a movement that seeks a partial change in society. (first used: 6. Sort movements by aim: Aberle's four types)
Transformative movement — In Aberle's model, a movement that seeks a total change in society, often taught as a revolutionary movement. (first used: 6. Sort movements by aim: Aberle's four types)
Relative deprivation theory — The theory that people organize into movements when they feel deprived compared with what they expected or with what others have. (first used: 7. Ask why movements rise and how they age)
Resource mobilization theory — The theory, from McCarthy and Zald, that a movement's success depends on the money, time, people, and organization it can marshal. (first used: 7. Ask why movements rise and how they age)
Political process theory — The theory that a movement's chances rise and fall with openings and closings in the political system around it. (first used: 7. Ask why movements rise and how they age)
Framing — The way a movement presents an issue so that people see a problem, a solution, and a reason to act, through diagnostic, prognostic, and motivational frames. (first used: 7. Ask why movements rise and how they age)
New social movement theory — The theory that addresses movements in postindustrial societies organized around identity, quality of life, and values rather than around class alone. (first used: 7. Ask why movements rise and how they age)
Movement life cycle — A commonly taught model of the stages a social movement passes through: emergence, coalescence, bureaucratization or institutionalization, and decline. (first used: 7. Ask why movements rise and how they age)
Social change — The transformation of a society's culture, structure, and institutions over time. (first used: 8. Name the engines of change and read them three ways)

Summary

A population changes through fertility, mortality, and migration.
Birth and death rates are per 1,000 people a year; natural increase is births minus deaths.
Every move has push factors and pull factors.
The total fertility rate is synthetic: children per woman at current rates, not a count.
Momentum can bring more births even as the rate falls.
The demographic transition is a four-stage model; Malthus predicted positive checks.
The concentric-zone model and Wirth's urbanism describe city growth and city life.
Collective behavior is spontaneous and brief; a social movement is organized and lasting.
Aberle sorts movements by whom and how much they seek to change.
Five theories and a life cycle explain why movements rise and how they age.
The global total fertility rate fell from 4.9 in the 1950s to 2.3 in 2023.

Check your understanding

Work these before looking at the answers — they are ungraded, and the answers (with reasoning) are at the bottom of the page.

An illustrative county of 80,000 people records 960 births and 720 deaths in one year. Find the crude birth rate, the crude death rate, and the natural increase, each per 1,000 people.
In an illustrative country, the age-specific birth rates for seven five-year age groups are 10, 60, 100, 80, 30, 15, and 5 births per 1,000 women a year. What is the total fertility rate?
Sort each illustrative movement into one of Aberle's four types: (a) a group that asks the state legislature to raise the minimum age for a driver's license; (b) a campaign urging people to drink more water each day; (c) a movement that seeks to abolish private property and rebuild the whole economy.
A classmate says, "The birth rate in my illustrative hometown fell, so there must be fewer babies there now." What can the falling rate tell you, and what can it not?

Answers (worked reasoning — read after attempting)

Crude birth rate: 960 ÷ 80,000 × 1,000 = 12 births per 1,000 people. Crude death rate: 720 ÷ 80,000 × 1,000 = 9 deaths per 1,000 people. Natural increase: 12 − 9 = 3 per 1,000 people a year, before counting anyone who moved in or out.
Add the rates: 10 + 60 + 100 + 80 + 30 + 15 + 5 = 300 births per 1,000 women for one year of each age group. Multiply by five years per group: 300 × 5 = 1,500 births per 1,000 women. Divide by 1,000: 1,500 ÷ 1,000 = 1.5 children per woman.
(a) Reformative: a partial change in society, one law. (b) Alterative: a partial change in individuals, one habit. (c) Transformative: a total change in society.
A falling rate says each woman of childbearing age is having fewer births at current rates. It cannot tell you the number of babies, because that also depends on how many women are of childbearing age. If that group grew, births could rise even as the rate fell; that is population momentum, so the classmate has read a rate as a count.

Next up in this module: the Readings & Resources page, the lecture tutorial, the practice set, the quiz, the discussion, and the assignment — and next week, the finals week, brings the Final Practice Exam and the final, with no new model to learn.

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