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EconViz Study Guide: Shifts vs. Movements

One rule to hold onto across every framework: a shift moves the curve itself (something on the right-hand side of its equation changed); a movementjust slides the equilibrium point along a curve that hasn't moved (a variable on the curve's own axes changed).

IS-LM-PC

IS: Investment-Savings curve.LM: Liquidity-Money curve.WS: Wage-Setting curve.PS: Price-Setting curve.PC: Phillips Curve.

Fiscal policy (IS shifts)

Government spending / taxes move the IS curve left/right. Since the central bank targets the policy rate directly (the LM curve is horizontal here), output moves but the interest rate does NOT — output slides along the unchanged LM curve.

Monetary policy (LM shifts)

The central bank raises/cuts the policy rate, shifting the horizontal LM curve up/down. Output then moves along the unchanged IS curve.

Demand shocks → movement along the PC

Any IS or LM shock changes the output gap, which moves the economy ALONG the existing Phillips Curve. The PC itself does not move.

Supply shocks / expectations → the PC itself shifts

A cost-push shock or a change in inflation expectations shifts the whole PC up/down, independent of the current output gap.

WS-PS → the natural rate, not actual output

A WS or PS shift changes the natural rate of unemployment (and so the natural level of output Yn) without moving actual output Y directly. Since the output gap is Y − Yn, this still shows up as a MOVEMENT along the PC, because Yn — not Y — moved.

AD-AS

AD: Aggregate Demand curve.SRAS: Short-Run Aggregate Supply curve.LRAS: Long-Run Aggregate Supply curve.

Demand shocks → movement along SRAS

Fiscal/monetary policy shifts AD left/right. SRAS is unchanged, so output and the price level move together along the existing SRAS.

Supply shocks → SRAS shifts (stagflation)

A cost-push shock shifts SRAS up/left. AD is unchanged, so output falls while the price level rises — the classic stagflation pattern.

Long-run growth → LRAS shifts

Productivity growth shifts the vertical LRAS right, permanently raising potential output. SRAS gradually drifts to realign.

Mundell-Fleming (IS-LM-BP)

IS: Investment-Savings curve.LM: Liquidity-Money curve.BP: Balance of Payments curve.

Floating exchange rate

Fiscal policy is fully CROWDED OUT by exchange rate movements (no lasting effect on output). Monetary policy is fully EFFECTIVE.

Fixed exchange rate

Fiscal policy is fully EFFECTIVE (the central bank must accommodate to defend the peg). Monetary policy is POWERLESS (any attempted change gets reversed by capital flows).

BP curve

Horizontal at the world interest rate r* under perfect capital mobility — capital flows instantly to equalize domestic and foreign returns.

Solow Growth Model

f(k): Per-worker production function in the Solow model: y = A·k^α.s·f(k): Investment per worker: the savings rate (s) times output per worker.(δ+n)·k: Breakeven investment per worker: the amount of investment needed just to keep capital per worker constant, offsetting depreciation (δ) and the dilution of capital as the workforce grows (n).

Steady state: where investment meets breakeven

The economy converges to k* where s·f(k) = (δ+n)·k. Below k*, investment exceeds breakeven so capital accumulates. Above k*, breakeven exceeds investment so capital declines. Both forces push toward k*.

Higher savings rate → higher k* and y*

A rise in s shifts the investment curve s·f(k) upward. At the old k*, investment now exceeds breakeven, so capital accumulates to a new higher steady state. The long-run level of output per worker rises, but the growth RATE returns to zero — the Solow model has no permanent growth effect from a savings change.

Higher population growth or depreciation → lower k*

Either shock steepens the breakeven line (δ+n)·k. More investment is required just to maintain capital per worker, so the steady state moves to a lower k*. Output per worker falls even though total output may be higher.

TFP shock (A↑) → both curves shift up

Higher TFP raises f(k) and s·f(k) simultaneously. The new steady state has higher capital AND higher output per worker — and unlike a savings increase, the direct productivity gain also raises output at every k, so the total effect on y* is larger.

Keynesian Cross (ZZ-NX)

ZZ: The demand curve in the Keynesian Cross: Z = C + I + G + NX, plotted against output (Y).45°: The equilibrium-identity line where planned spending equals output (Z = Y).NX: Net Exports curve: exports minus imports, plotted against output (Y).

Equilibrium

Equilibrium output is where the ZZ (demand) curve crosses the 45° line (Z = Y).

Domestic demand shock

A rise in investment/government spending shifts ZZ up — output rises, but the trade balance WORSENS, since higher income pulls in more imports (a movement along the unchanged NX curve).

Export demand shock

A rise in foreign demand for exports shifts BOTH ZZ and NX up (since net exports are part of demand). Output rises and the trade balance can IMPROVE even as output rises — the opposite of a domestic-demand-driven expansion.