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Week 11 · Lecture outline

Week 11 — Lecture Outline · Monetary Policy, Interest Rates & Aggregate Demand: The Transmission Mechanism

Principles of Macroeconomics · ECON 2 Fall 2026 · Prof. Ashford Fictional sample

Course: Principles of Macroeconomics (ECON 2) · Silver Oak University (fictional sample) · Prof. Ashford
Objective 7 — money, banking, the Fed & monetary policy; the transmission mechanism from the money supply to interest rates, investment, and aggregate demand · SLO A & B
Meeting pattern: two 75-min sessions (≈150 min). Veterans Day, Wed Nov 11 — no class this week; sessions fall Mon & Thu. Segment minutes below total ~150 — scale to your room.

The deck (E), the tutorial (C), and the workshop (P) all teach from this outline. Every number here is pre-computed and independently verified (see the verified box in §4).

Week at a glance
Big question By what chain of events does a Fed action to change the money supply end up changing real GDP and the price level — and what happens if that chain breaks down?
By week's end students can (1) trace the monetary-transmission mechanism link by link (MS → r → I → AD → P & Y); (2) distinguish expansionary from contractionary monetary policy and predict the P/Y outcome of each; (3) explain why an interest-rate change moves investment (and consumption, more mutedly) rather than working through the fiscal channel; (4) name the role of lags and expectations, including the monetarist "long and variable lags" critique; (5) weigh, evenhandedly, whether monetary policy is closer to fine-tuning or a blunt instrument.
Key vocabulary monetary-transmission mechanism, expansionary monetary policy, contractionary monetary policy, interest-rate channel, investment demand, aggregate demand (AD), the multiplier (recap), inside lag, outside lag, "long and variable lags," rational/adaptive expectations (named), fine-tuning vs. rules
Materials whiteboard; the Week-11 readings/links; Desmos or a spreadsheet for the chain table; an approved chatbot
Timing note 8 segments ≈ 150 min across two sessions (Mon & Thu — no Wednesday session this week). Trim Segment 7 (interaction) if short on time.

Segment 1 — HOOK: "The Fed did something. Now what?" (12 min)

Open with a headline-style prompt: "Suppose you read: 'The Federal Reserve buys $100 billion in government bonds.' Does that headline, by itself, tell you anything about your job, your rent, or the price of groceries?" Let students sit with it — most will sense that something should happen but can't say what, exactly, or how many steps away it is.

Reframe: last week you built the money market and found a new interest rate. That's actually the SECOND-TO-LAST stop, not the destination. This week's whole job is to walk the rest of the way: interest rate → investment spending → aggregate demand → the price level and real output. That full path is the monetary-transmission mechanism, and once you can walk it forward, you can walk it backward for a rate hike too.

Segment 2 — PLAIN-LANGUAGE IDEA: five links, one chain (15 min)

Teach the whole chain in one sentence first, then unpack link by link:

Monetary transmission: the Fed changes the money supply → the interest rate moves the opposite way → interest-sensitive spending (mainly investment) moves the SAME way as the money supply → aggregate demand shifts → the price level and real output move together in that same direction.

Walk the five links as a numbered list, plain language first, before any numbers appear (numbers come in Segment 3):

  1. The Fed acts — say it buys bonds (an open-market purchase, from Week 10).
  2. The money supply rises, which (recall Week 10) lowers the interest rate — more loanable funds chasing the same borrowers pushes the price of borrowing down.
  3. Investment responds — firms that were on the fence about a new factory, a new delivery van, or new software now find the loan cheaper, so planned investment spending (I) rises. (One line, evenhandedly: consumer spending on big-ticket, credit-financed items — cars, homes — often responds too, but investment is the textbook channel principles courses emphasize; we'll say "mainly investment" and note consumption as a secondary channel.)
  4. Aggregate demand shifts — investment is one of AD's four components (C + I + G + NX), so a rise in I shifts the whole AD curve to the right (recall the multiplier from Week 7: the initial ΔI gets multiplied into a larger ΔY).
  5. Prices and output respond — walking up the fixed SRAS curve, a rightward AD shift raises both the price level (P) and real output (Y).

Memory hook: "Buy bonds, rate drops, spending pops, demand shifts, prices and output both lift." Run the sentence backward for a sale of bonds and you have contractionary policy for free — that's the payoff of learning the chain as a chain, not five disconnected facts.

Segment 3 — WORKED EXAMPLE #1: the full chain, numeric, every link shown (25 min)

Set it up on the board and do every step out loud — this is the week's anchor scenario.

Starting point (carried over from Week 10): money supply MS = $600 billion, equilibrium interest rate r = 6%.

Step 1 — The Fed buys bonds. Open-market purchase raises the money supply from $600B to $700B.

Step 2 — The interest rate falls. From Week 10's money-market model, this expansion in MS moves the equilibrium down the (unchanged) money-demand curve to r = 5% — a 1-percentage-point drop.

Step 3 — Investment responds. This course's engineered rule: investment rises $20 billion for every 1-percentage-point drop in the interest rate. A 1-point drop (6% → 5%) → ΔI = +$20 billion.

Step 4 — The multiplier does its work. Recall the spending multiplier from Week 7: at MPC = 0.8, the multiplier = 1/(1 − 0.8) = 5. The initial $20B injection in investment ripples through the economy: ΔY = ΔI × multiplier = $20B × 5 = +$100 billion.

Step 5 — Read it on the AD–AS diagram. That $100 billion of new spending shows up as aggregate demand shifting right. Walking up the fixed SRAS curve from the old equilibrium: the price level rises (P↑) and real output rises (Y↑) — both move the same direction, together, because AD moved right along a fixed SRAS.

✅ VERIFIED NUMBERS (pre-computed; do not recompute live)

  • MS: $600B → $700B (Fed buys bonds).
  • Interest rate: 6% → 5% (a 1-point fall).
  • ΔI = 1 point × $20B/point = +$20B.
  • Multiplier at MPC 0.8 = 1/(1−0.8) = 5.
  • ΔY = $20B × 5 = +$100B.
  • AD shifts right; P↑, Y↑ (walking up SRAS).

Say it in words (the SLO-A habit): "The Fed bought bonds, the money supply grew by $100 billion, the interest rate fell one point, that made investment $20 billion more attractive, and the multiplier turned that $20 billion into $100 billion of extra real output — with prices ticking up along the way." State each link out loud before moving to the next; skipping a link is the single most common transmission-mechanism error.

Segment 4 — CONTRACTIONARY POLICY: reverse EVERY arrow (18 min)

The whole chain runs in reverse for contractionary monetary policy — same links, opposite signs, nothing new to learn.

Walk it explicitly, arrow by arrow, contrasting with Segment 3:

  • The Fed sells bonds (instead of buying) → the money supply falls (instead of rising) → the interest rate rises (instead of falling) → investment falls (instead of rising) → AD shifts left (instead of right) → walking down the fixed SRAS, the price level falls and real output falls (P↓, Y↓ — instead of P↑, Y↑).

Numeric mirror (same magnitudes, opposite direction): if the Fed instead sold bonds to push MS from $600B down to $500B, the interest rate would rise from 6% to 7% (a 1-point rise); ΔI = −$20B; ΔY = −$20B × 5 = −$100B; AD shifts left; P↓, Y↓.

Misconception to kill: students (and chatbots) often get the FORWARD chain right but then, asked for the reverse case, only flip the last arrow (P and Y) while leaving an earlier link (like the interest-rate direction) unchanged. Every single arrow flips, not just the ending. Make students say the whole reversed chain out loud, link by link, the same way they said the forward one.

One qualitative caveat, named honestly: the chain can weaken if banks hoard excess reserves instead of lending them out — if a bank sits on new reserves rather than making loans, the money-supply expansion doesn't fully reach borrowers, and Link 3 (investment response) can be smaller than the clean $20-billion-per-point rule assumes. This is a real-world qualification on an otherwise clean teaching chain, not a reason to abandon the model.

Segment 5 — LAGS, EXPECTATIONS & THE FINE-TUNING DEBATE (20 min)

Name two real-world complications, factually, before the debate:

  • Lags. Monetary policy doesn't work instantly. There's an inside lag (time to recognize a problem and decide to act) and an outside lag (time for the rate change to work through the chain you just traced — borrowing, building, hiring). Economists in the monetarist tradition, associated with Milton Friedman, have long argued that these lags are "long and variable" — long enough, and unpredictable enough, that by the time a policy's effects arrive, the economy's problem may have already changed or reversed on its own. (Named factually as an idea associated with Friedman's monetarist critique — no invented quotation.)
  • Expectations. How households and firms expect the Fed to act, and expect prices to move, can shape their behavior today — sometimes blunting or accelerating a policy's effect before the "mechanical" chain even finishes. (Named at the level this course covers it: expectations matter and are studied formally in more advanced courses; we don't derive rational- vs. adaptive-expectations models here.)

The debate — present BOTH sides at full strength (this is the discussion topic, so plant it firmly and evenhandedly here):

  • The case for active "fine-tuning": advocates in the Keynesian tradition argue the Fed has real, usable tools and enough information to lean against recessions and overheating as they emerge — better an imperfect nudge than no response at all while a downturn deepens.
  • The case for skepticism / rules over discretion: advocates in the monetarist/classical tradition argue that "long and variable lags," imperfect information, and the risk of overcorrecting (fixing yesterday's problem after today's has already changed) make discretionary fine-tuning more likely to add instability than remove it — favoring simpler, predictable rules instead.

Neither side is declared correct here — Discussion 11 is where students argue it out with the same evenhandedness this course keeps all term.

Segment 6 — TECHNOLOGY WORKFLOW + AI-CRITIQUE (18 min)

Live demo (Desmos or spreadsheet): build a simple chain table — columns for MS, r, ΔI, ΔY (after the multiplier), AD direction, and P/Y outcome — and fill in this week's anchor scenario live, then the contractionary mirror.

AI-critique moment (do this with the class): Ask an approved chatbot: "If the Fed lowers the interest rate from 6% to 5%, and investment rises $20 billion for every 1-point interest-rate drop, and the spending multiplier is 5, what happens to real GDP, and what happens to the price level? Now tell me what happens if the Fed instead RAISES the rate from 6% to 7%." Then audit it together: the right forward answer is ΔY = +$100B, P↑, Y↑; the right reverse answer is ΔY = −$100B, P↓, Y↓. Chatbots commonly make three errors here: (1) using the wrong multiplier (grabbing 1/RR — the money multiplier from Week 9 — instead of 1/(1−MPC), the spending multiplier); (2) skipping the interest-rate link entirely and jumping straight from "Fed action" to "AD shifts," which hides where the $20B even came from; (3) on the reverse case, flipping only the P/Y ending while leaving the interest-rate direction unchanged from the forward case. Make the class catch each error and restate the full, correctly reversed chain. The habit all term: the tool drafts, you judge.

Segment 7 — INTERACTION: mini-debate (12 min)

Split the room (or pairs) into "fine-tuners" and "skeptics." Give each side 90 seconds to make the strongest version of its case using Segment 5's framing (Keynesian activist case vs. monetarist lags-and-rules case), then two rebuttal rounds. Debrief: the goal isn't to declare a winner — it's to notice that both sides accept the SAME mechanical chain (Segments 3–4) and disagree about something else entirely: how reliably and how quickly that chain operates in the real world. This directly previews Discussion 11.

Segment 8 — CALLBACKS, TEASE & THE WEEK'S WORK (10 min)

  • Callback: every link today connected to a prior week — the interest rate from Week 10's money market, the multiplier from Week 7's fiscal policy, and the AD–AS diagram from Week 5. Monetary transmission is where those three previously separate ideas finally meet.
  • Tease next week: "We've been treating the price level as something that just moves up or down along with output. Next week we zoom in on inflation itself and its relationship to unemployment — the Phillips curve — plus a second, older theory of the price level: the quantity theory of money."
  • The week's work: Lecture Tutorial (the five-link chain, forward and reversed), Practice (6 reps), Quiz 11, Discussion 11 ("Fine-tuning or blunt instrument?"), Assignment 11, and Workshop 11 ("Trace the Transmission Mechanism" — complete the chain table, then reverse it).

Instructor FAQ — common stumbles

  • "Isn't the transmission mechanism just the money market again?" No — the money market (Week 10) gets you to Link 2 (the new interest rate). Transmission is Links 3–5: how that rate change turns into a change in spending, then output, then prices. Treat Week 10 as "half the story."
  • "Which multiplier do I use here — 1/RR or 1/(1−MPC)?" 1/(1−MPC), the spending multiplier, always — money creation (1/RR, Week 9) is a completely separate idea about how banks expand the money supply itself, not about how a given change in spending ripples through the economy.
  • "Does the interest rate change shift investment demand, or move along it?" For THIS course's purposes, treat the interest-rate change as causing investment spending to change (the mechanism we're tracing) — don't confuse this with Week 10's separate point that an interest-rate change moves along money demand rather than shifting it. Different curve, different rule.
  • "If the chain is this clean, why do economists disagree about monetary policy at all?" Because the disagreement isn't about the mechanical chain — both schools of thought accept Segments 3–4 as written. The argument is about lags, information, and reliability: can policymakers time it right in practice, or does trying to fine-tune do more harm than good? That's a genuinely open, evenhandedly presented debate, not a settled fact.
  • "What if banks just sit on the new reserves instead of lending them?" Then Link 3 weakens — investment responds by less than the clean $20B-per-point rule, because the money never fully reaches borrowers. This is a real qualification, not a reason to throw out the model; note it and move on.
  • "Is consumption part of this chain too?" Investment is the textbook channel at the principles level, and it's what our numbers model. Consumer spending on big credit-financed purchases (cars, homes) often responds to rate changes too, as a secondary channel — worth a one-line mention, not a separate arithmetic pipeline.

~ Prof. Ashford's edition · Fall 2026 · built with thecoursemaker.com