Economic Growth: Sources, the Rule of 70, and Growth Policy

Objectives

• Students will be able to calculate doubling time using the Rule of 70 and compute real GDP per capita growth as real GDP growth minus population growth.
• Students will be able to distinguish economic growth (an outward shift of the PPC or a rightward shift of LRAS) from a recovery (a movement back toward the frontier).
• Students will be able to identify the sources of growth, physical capital, human capital, and technology, and explain diminishing returns and catch-up growth.
• Students will be able to evaluate which public policies raise long-run aggregate supply, including investment incentives, education, R&D, institutions, and open trade.
• Students will be able to draw a correctly labeled PPC or LRAS graph showing an increase in productive capacity.

Materials (all free, no student accounts needed)

• Lesson: Economic Growth
• Production possibilities graph sandbox
• Draw-the-graph FRQ practice
• Economic growth practice quiz
• Full practice test bank
• CED Topic 5.6 page

Five-minute warm-up, no prep

Open one of these on the projector. Students say what they think happens to price and quantity before anything moves, lock it in, and then the graph plays out step by step. No accounts, nothing graded or stored.

• Crowding Out: Government Deficit Borrowing
• A Rise in National Saving
• US Interest Rates Rise: The Dollar Appreciates

Warm-up (8 min)

• Put this on the board: in 1960 South Korea and Ghana had about the same GDP per person, and by 2020 South Korea's was more than 20 times higher. Ask students to jot down one reason.
• Cold-call three students for their reasons and sort them on the board into capital, skills and education, and technology without naming the terms yet.
• Tell them today's question is why some economies pull away over a lifetime while others stall.

Direct instruction (32 min)

• Define economic growth precisely: a sustained rise in real GDP per capita. Contrast it with a rise in nominal GDP, which could be inflation, and with a rise in total GDP that population growth cancels out.
• Teach the Rule of 70 on the board: doubling time equals 70 divided by the annual growth rate. Work 2% (35 years) and 7% (10 years) so the compounding gap is visible.
• Run the two-country example from the lesson: at 2% versus 5% growth from the same $10,000 start, show how one generation later Country B is nearly three times richer.
• Lay out the three sources: physical capital (tractors, factories), human capital (skills, education, health), and technology or total factor productivity (doing more with the same inputs). Use the farmer-with-a-tractor example.
• Explain diminishing returns to capital and catch-up growth: the tenth tractor adds far less than the first, so capital-poor countries can grow faster than capital-rich ones.
• List the growth policies: investment incentives, education and health spending, R&D funding, strong property rights and institutions, and open trade. Tie each back to which source it strengthens.

Guided practice (30 min)

• Project /sandbox/ppc. Point to a spot inside the curve and a spot on the curve, then ask the class which one represents a recession with idle resources.
• Shift the whole PPC outward and cold-call: is this a recovery or is this growth? Nail the distinction: growth is a shift OF the frontier, a recovery is a move back TO it.
• Ask what real-world change would cause this outward shift and take answers until capital, labor, human capital, and technology are all on the board.
• Switch framing: tell students the same event on an AD-AS graph is a rightward LRAS shift, and have them sketch that beside the PPC in their notes.
• Open /frq-practice/draw to the Long-Run Growth scenario, read the prompt aloud, and have a volunteer identify which curve moves and in which direction before revealing the model answer.
• Do a 60-second whiteboard round: call out 'a one-year tax rebate to boost spending' and have students hold up G for growth or N for not-growth. Confirm demand stimulus is not long-run growth.

Independent practice (25 min)

• Assign the 8 questions shown on /practice/economic-growth and circulate to catch anyone who thinks more capital always means faster growth.
• For targeted drill on the Rule of 70, per-capita growth (GDP growth minus population growth), and the convergence and diminishing-returns items, send students to the full bank on /practice-test.

Exit ticket

• On a card, calculate the doubling time for an economy growing at 3.5% per year using the Rule of 70.
• In one sentence, explain the difference between economic growth and a recovery from a recession, referencing the PPC.

Homework

• Work through the full economic-growth bank on /practice-test (choose the economic growth module).
• Read the 'Policies That Promote Growth' section of /macro/economic-growth and rank the five policy levers from most to least effective, with one sentence of justification.

Differentiation

• Support: give a fill-in-the-blank Rule of 70 template and a labeled diagram showing the shift-of versus move-to distinction.
• Support: provide a sorting card matching examples (a new seed variety, a coding boot camp, a new factory) to physical capital, human capital, or technology.
• Extension: assign the resource-curse and Soviet-stagnation questions and have students explain why capital accumulation alone eventually stalls.
• Extension: have students compute how much richer a 3% economy is than a 1% economy after 70 years and connect it to the compounding argument.

Misconceptions to head off

• Students call any increase in GDP economic growth. Correct it: growth is a sustained rise in REAL GDP per capita, since nominal increases can be inflation and population growth can cancel raw GDP gains.
• Students label a recovery from recession as growth. Correct it: returning to potential is a movement back to the PPC or AD-AS equilibrium, while growth is an outward shift of the PPC and a rightward shift of LRAS.
• Students assume more physical capital always means faster growth. Correct it: capital has diminishing returns, which is why capital-rich economies slow and capital-poor economies can catch up.
• Students treat demand-side stimulus as a growth policy. Correct it: AD shifts move output temporarily around potential, while only more resources or better technology raise potential output.