Lecture: Macroeconomic Schools & Policy Debates
Lecture script · about 15–20 minutes spoken · Week 15
Opening
Here's a puzzle worth saying out loud. Two economists study the same slowdown. One tells the government to spend more right away. The other says hold steady and let prices adjust. They both trained on the diagram you've drawn all course. So why the opposite advice?
Think about who's listening. A restaurant owner is deciding whether to hire two more cooks or wait. A nursing student is wondering whether the clinic jobs on offer now will still be open next year. A voter is weighing a candidate's plan for the national debt. Each of them hears both economists and has to decide whom to believe.
Here's where we are. In Week 6, Business Cycles & Short-Run Fluctuations, you measured the output gap. In Week 7, Fiscal Policy, you met the spending multiplier, the deficit, and the debt. In Week 11 you traced the chain from money to output and heard the fine-tuning versus rules debate. In Week 12 you met the Phillips curve and the quantity equation. This lecture adds no new model. It reads the models you already own through two lenses.
Here's the plan. I'll start from one shared picture, then make each school's case at full strength and put them side by side. Then I'll state what both schools accept, compute the debt and deficit ratios, and meet inflation targeting. We'll argue one live question from both sides, and we'll finish by looking back over the whole course. The dollar figures in this lecture are illustrative, built for this course, and measured in billions of dollars.
1. The same gap, two readings
Picture two doctors reading the same blood test. They agree on every number. They may still disagree on whether to treat now or wait and watch.
Economists work the same way. Here's the term. A school of thought is a group of economists who share a way of reading the evidence and a set of policy instincts. In macroeconomics the two main ones are the Keynesian tradition and the classical and monetarist tradition.
Now the shared picture, from the course's illustrative output-gap economy. Potential output is 1,000. Actual output is 950. Subtract, and the recessionary gap is 50. Divide 50 by 1,000 and multiply by 100, and the gap is 5 percent of potential. On the diagram, the crossing of aggregate demand and short-run aggregate supply sits to the left of the vertical long-run line.
Both schools compute exactly that. Their argument starts after the equals sign.
Pause and try this. Do the two schools disagree about the size of this gap?
Think about where the argument really starts.
Here's the answer. No. Both compute a gap of 50, or 5 percent of potential. They disagree about how fast the gap closes on its own and whether policy should push.
2. The Keynesian case
Think about the restaurant owner. Sales are down, but the menu prices are printed, the lease is signed, and the cooks' wages are set. None of that adjusts overnight.
Here's the term. The Keynesian tradition is the school of thought that stresses sticky prices and wages and aggregate demand as the driver of short-run swings, so an economy can stay stuck in a gap and active policy can help close it.
Its tool is activist policy: deliberate changes in government spending, taxes, or monetary policy, made case by case, with the aim of closing an output gap sooner than the economy would close it on its own. In a deep slump, its preferred lever is fiscal policy.
Let's size the lever in the simple model. The spending multiplier at an MPC of 0.8 is 5. The gap is 50. Divide 50 by 5, and the government needs 10 of new spending. Check it: 5 times 10 is 50, the size of the gap.
The risk this school names is a prolonged gap. Every month it stays open, people who want work can't find it, and output that could have been made is lost for good.
Pause and try this. Why does the Keynesian tradition think waiting is risky?
Connect it to sticky prices.
Here's the answer. Because sticky prices and wages fall slowly, the gap can last a long time. Waiting means more months of idle workers and lost output.
3. The classical and monetarist case
Now picture someone who has watched governments try to steer before. The worry isn't that policy does nothing. It's that the help arrives late and leaves a bill.
Here's the first term. The classical tradition is the school of thought that stresses flexible prices and wages in the long run and potential output as the economy's anchor, so an economy in a gap tends to correct itself without new policy. Flexible prices and wages adjust quickly when demand or costs change.
Here's the second. The monetarist tradition is the school of thought, associated with Milton Friedman, that warns monetary policy works with long and variable lags and so favors steady, predictable rules over frequent adjustments.
This column names two risks. The first is lags. If the gap closes on its own before the spending lands, the push moves output past potential and opens an inflationary gap. The second is crowding out: government borrowing pushes up interest rates and squeezes private investment, so the net gain shrinks. Its preferred lever is steady monetary policy that follows a rule.
Pause and try this. Does the classical tradition say policy never affects output?
Recall what it accepts about the short run.
Here's the answer. No. It accepts that money and spending move output in the short run. Its worry is timing, predictability, and the debt.
4. The schools table
Put the two columns side by side and ask each one the same questions. How fast do prices adjust? Keynesian: slowly. Classical and monetarist: fairly quickly in the long run. Can the economy get stuck? Keynesian: yes. Classical: it tends to heal. Activism or rules? Keynesian: act case by case. Monetarist: follow a rule. The named risk? A prolonged gap, against lags and crowding out. Each answer is the strongest version of its side.
Now two wrong turns. The first treats sticky versus flexible prices as a political stance. It isn't. How fast prices adjust is an empirical question that evidence can test.
The second wrong turn mixes up rules versus discretion, the debate over whether policymakers should follow a policy announced in advance or choose a fresh response to each situation, with fiscal versus monetary. They're separate questions. Income taxes and unemployment insurance that move with the economy are automatic stabilizers, a fiscal rule. A central bank that leans against every wobble is fine-tuning, which is monetary discretion.
Pause and try this. A new spending bill passed to fight a slump: fiscal or monetary, rule or discretion?
Ask who wields it, then ask whether it was chosen case by case.
Here's the answer. It's fiscal, because the legislature passes it. And it's discretion, because it's a fresh choice made for this slump.
5. The agreed ground
Not everything here is a debate. Here's the term. The agreed ground is the positive results that both schools of thought accept, stated plainly rather than argued both ways.
The first result: the long-run Phillips curve is vertical. In the course's illustrative economy, holding unemployment at 4 percent buys 6 percent inflation. Once people expect 6 percent, the short-run curve shifts up. The economy settles at 5 percent unemployment with inflation still at 6 percent, back at the natural rate.
The second: sustained inflation is, in the long run, a monetary matter. With velocity at 4 and real output at 1,000, raise the money supply 10 percent, from 500 to 550. The price level rises from 2 to 2.2, also 10 percent. And the growth form says inflation is about money growth minus output growth: 8 percent minus 3 percent, or about 5 percent.
The third: the short run and the long run differ. In Week 11's chain, an expansionary move raised real output by 200 in the short run. In Week 12's separate quantity-equation example, real output stays at 1,000 in the long run when money rises.
Pause and try this. Should you write "some economists think the long-run Phillips curve is vertical"?
Ask whether this is contested or agreed.
Here's the answer. No. It's agreed ground, so you state it plainly. Evenhandedness belongs to the contested questions.
6. The ratios both schools share
Is a debt of 1,000 big? It depends on the size of the economy. A lender asks the same thing about a family's debts and its income.
Use the course's illustrative budget. Revenue is 400, spending is 450, the starting debt is 1,000, and GDP is 1,250. The deficit is 450 minus 400, which is 50, a flow.
Here's the first term. The deficit-to-GDP ratio is one year's budget deficit divided by that year's GDP, times 100. Divide 50 by 1,250 and multiply by 100, and you get 4 percent.
Here's the second. The debt-to-GDP ratio is the national debt at a point in time divided by GDP, times 100. Divide 1,000 by 1,250, times 100, and you get 80 percent at the start of the year. Add the deficit, and the debt is 1,050, a stock. Divide 1,050 by 1,250, times 100, and the ratio is 84 percent. With GDP held fixed, the ratio climbed from 80 to 84 percent, the same 4 as the deficit ratio. A deficit adds to the debt. That's arithmetic.
Pause and try this. A classmate puts the debt where the deficit belongs and reports a deficit ratio of 80 percent. What went wrong?
Ask which number is the flow.
Here's the answer. The classmate used the stock. 80 percent is the debt ratio, and it's 20 times the true deficit ratio of 4 percent.
7. The ratios through each column
Both schools accept 4, 80, and 84 percent. They differ on how much those numbers should worry you.
The Keynesian reading: a deficit in a slump is a tool. Borrowing puts idle people to work, crowding out is small when saving sits unused, and as output recovers, the ratio can fall again.
The classical and monetarist reading: a rising ratio is a real cost. Government borrowing competes with private borrowers, pushes up interest rates, and crowds out the investment that builds future output. It also leaves a larger bill for future taxpayers, who had no vote on the choice.
So the ratio is a fact, and the worry is a weight. How big crowding out really is can be tested. How to weigh jobs now against burdens later is a question of values.
Pause and try this. Does a debt ratio of 84 percent prove one school right?
Separate the number from the judgment.
Here's the answer. No. Both schools compute 84 percent the same way. Whether it's too high depends on disputed evidence and on values.
8. Inflation targeting
Imagine a bakery owner signing a long lease. Rent, flour, and wages all depend on how fast prices rise, so a central bank that announces its plan makes that guess easier.
Here's the term. Inflation targeting is a policy framework in which a central bank announces a numerical goal for the inflation rate and sets its tools to keep inflation near that goal over time.
That's the fact. Each school finds something in it. Rules supporters like that the goal is announced in advance, because a believable goal anchors expected inflation, the force that shifts the short-run Phillips curve. Discretion supporters like that the goal holds over time, not every month, which leaves room to respond to a slump.
Pause and try this. Does an inflation target mean inflation sits exactly at the goal every month?
Think about the words "over time".
Here's the answer. No. Shocks push inflation away from the goal, and policy pulls it back with lags. The goal is for inflation over time.
9. One live question, both columns
Now the method on a real question: should a government borrow to close a recessionary gap? Write each claim on its own line, say which column it supports, and label it.
"In the simple model, 10 of new spending closes a gap of 50." Positive, a model result, Keynesian. "A deficit of 50 raises the debt ratio from 80 to 84 percent." Positive, arithmetic both schools accept. "Sticky prices make a gap last." Positive, but the evidence is disputed. "Lags and crowding out shrink the effect." Positive, also disputed. "Shortening a spell of joblessness is worth a higher debt ratio." Normative, Keynesian. "A lower debt burden is worth a slower recovery." Normative, classical and monetarist.
No diagram settles those last two lines. They rest on what you value. This course gives you both columns and leaves the verdict to the evidence and your own values.
Pause and try this. "Future taxpayers shouldn't pay for this recovery." Positive or normative?
Ask whether evidence could settle it.
Here's the answer. Normative. It says what ought to happen and rests on a value about fairness across generations.
10. The habits you carry forward
You started this course asking what the whole economy even means. You measured it, built models, and used them on policy. Four habits carried you.
Real versus nominal: nominal GDP of 1,100 against real GDP of 1,000 gave a deflator of 110. Movement along versus shift: government spending shifted aggregate demand right, from 800 to 900 in output and from 12 to 13 in the price level. The money multiplier versus the spending multiplier: 10 in banking, 5 in fiscal policy. And positive versus normative: "the debt ratio rose to 84 percent" is a fact, while "the debt ratio is too high" is a judgment.
Pause and try this. A headline says government spending pushed prices and output up. Which habit tells you the curve that moved?
Name the curve before you name the habit.
Here's the answer. Movement along versus shift. New spending shifts aggregate demand right, so the price level and real output rise together.
Closing
Let me pull it together, in the order we built it. Both schools read the same gap of 50, or 5 percent of potential. The Keynesian tradition sees sticky prices and a gap that can last, and it acts. The classical and monetarist tradition sees flexible prices, lags, and crowding out, and it prefers rules. Rules versus discretion is a different question from fiscal versus monetary. The agreed ground stays plain: a vertical long-run Phillips curve, inflation as a monetary matter in the long run, and a short run that differs from the long run. The deficit ratio is 4 percent and the debt ratio climbs from 80 to 84 percent. Inflation targeting names a goal and steers toward it over time. On any live question, you label each claim and leave the values to the reader. And four habits carry you through.
Next in this module, you'll find the slide deck, the Readings & Resources page, the lecture tutorial, the practice set, and the quiz, then the discussion, the assignment, and the Model Workshop. After that comes the finals week, with the Final Practice Exam and the final. There's nothing new to learn there, only the habits you've built.
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