Demand-Oriented Economic Policy and the IS-Curve Model

Foundations of Keynesian Theory and Demand Fluctuations

• Central Argument of Keynesian Theory: A primary tenet of the theory developed by John Maynard Keynes is that short-term fluctuations in production are primarily caused by fluctuations in aggregate demand.
• Volatility of Economic Components: Keynes observed that investment activity by firms exhibits much higher volatility in the short term compared to expenditures by private households or the government.
• The Primacy of Investment Demand: Due to this high volatility, Keynes maintained the view that investment demand exerts the strongest influence on production levels.
• Origin of the IS-Curve: This observation served as the justification for developing the IS-Curve, which serves as a tool to represent fluctuations in investment demand. While originally focused on investment, the IS-Curve is now applied generally to all fluctuations in macroeconomic demand.
• Statistical Context (Annual Growth Rates): Historical data indicates significant variance in growth rates (measured in percentage):
  • Investments: Historically the most volatile, with swings ranging from approximately $-20\%$ to $+15\%$.
  • Private Household Expenditures: Generally stable, fluctuating within a narrower range (roughly $0\%$ to $5\%$).
  • Government Spending: Also shows stability relative to investment, typically staying within the $0\%$ to $5\%$ growth range.

The Investment Function and Its Determinants

• Transition from Exogenous to Endogenous Investment: Early models often treated investment as an exogenous variable (determined outside the system). In this refined model, investment is treated as endogenous, meaning it depends on specific economic variables.
• Bestimmungsgründe (Determinants) of Investment: There are two primary drivers for a firm's decision to invest:
  1. Level of Demand ($Y$): There is a positive correlation between demand and investment. As demand increases, firms seek to expand their production capacity, leading to higher investment spending ($Y \uparrow \implies I \uparrow$).
  2. The Interest Rate ($i$): There is a negative correlation between the interest rate and investment. This interest rate represents the cost of financing, whether through internal capital or external credit/bonds. For this model, the credit market interest rate is the decisive factor ($i \uparrow \implies I \downarrow$).
• Mathematical Representation: The investment function is formulated as:     $I = I(Y, i)$
  • The $+$ sign following the variable $Y$ indicates that investment increases with rising demand.
  • The $-$ sign following the variable $i$ indicates that a rising interest rate reduces investment activity.
• Integration into the Goods Market Equilibrium: Substituting the investment function into the total demand function results in the following equilibrium condition (where $Y = D$):     $Y = c_0 + c_1(Y - T) + I(Y, i) + G$
  • $c_0$: Autonomous consumption.
  • $c_1(Y - T)$: Consumption dependent on disposable income (income minus taxes).
  • $I(Y, i)$: Endogenous investment function.
  • $G$: Government spending.

Graphical Analysis of Investment and the IS-Curve

• The Investment Curve: Graphically, the interest rate ($i$) is plotted on the vertical axis and the investment volume on the horizontal axis. Since it functions like a demand curve for capital, it is negatively sloped.
  • Movement Along the Curve: Occurs when the interest rate changes, directly affecting the investment volume.
  • Shifts of the Curve: The entire investment function shifts when there is growth or shrinkage in the GDP ($Y$).
• The IS-Curve Defined: The IS-Curve represents the combination of the goods market and the investment function. It illustrates changes in the goods market equilibrium as a function of the interest rate.
• The Mechanism of the IS-Curve Slope:
  1. An increase in the interest rate ($i$) leads to a decrease in investment ($I$).
  2. A decrease in investment leads to a reduction in autonomous spending by an amount $\Delta I = I(i_{new}) - I(i_{old})$.
  3. This reduction in spending leads to a decrease in total income/production ($Y$) via the multiplier effect.
• Economic Interpretation: In principle, the IS-Curve acts as a demand curve for the overall economy by linking a "price" (the cost of credit/interest rate) with a quantity (BIP/production). It represents a set of possible equilibrium points.

Shifts in the IS-Curve

• General Rule: Any factor that shifts aggregate demand (which aren't interest rate changes) will shift the IS-Curve.
• Specific Factors:
  • Government Spending ($G$): An increase in state expenditures shifts the IS-Curve to the right.
  • Taxes ($T$): A reduction in taxes increases disposable income, shifting the IS-Curve to the right, which increases BIP. Conversely, a tax increase shifts it to the left.
  • Demand Shocks: Any sudden collapse in demand (e.g., loss of consumer confidence) shifts the curve to the left.
• Fiskalpolitik (Fiscal Policy) Limitation: While fiscal policy (like tax cuts) shifts the IS-Curve and changes the BIP, in this specific model, it has no direct influence on the credit market interest rates themselves ($i$ remains unchanged unless the central bank reacts).

Monetary Policy and the Role of the Central Bank

• Leitzins (Policy Rate): Demand-oriented policy incorporates the role of the Central Bank via the policy rate ($i^*$).
• Interest Rate Parity Assumption: While the credit market rate ($i$) is technically distinct from the policy rate ($i^*$), the model assumes for simplicity that they correspond ($i \approx i^*$).
• Policy Goal: The Central Bank attempts to set a policy rate that enables the economy to reach its natural BIP ($Y_n$), the level where supply and demand are balanced.
• The Zinslinie (Interest Line): In the $(Y, i)$ diagram, the central bank's policy is represented as a horizontal line at the level of the policy rate.
• Central Bank Actions:
  • Rate Hike: The interest line shifts upward, moving the equilibrium along the IS-Curve to the left, decreasing BIP from $Y_0$ to $Y_1$.
  • Rate Cut: The interest line shifts downward, increasing the BIP.

Demand Shocks and Policy Responses

• Definition of Demand Shock: A change in macroeconomic demand triggered by factors not explicitly contained in the standard demand function. These can occur suddenly or develop over several years.
• Examples of Shocks:
  • Policy decisions (new taxes or sudden spending changes).
  • Financial innovations (e.g., credit cards allowing faster spending of money).
• Scenario: Leftward Shift of IS-Curve: A negative shock reduces BIP from $Y_n$ to $Y_1$.
• Government Response (Fiscal Policy): The government can increase spending ($G$) to shift the IS-Curve back to its original position. Warning: This requires public financing.
• Central Bank Response (Monetary Policy): The Bank can lower the policy rate from $i^*$ to $i_1$. This moves the interest line down until it intersects the shifted IS-Curve at the original natural production level ($Y_n$).

Case Studies: Global Financial Crisis and Euro Crisis

The 2008 Global Financial Crisis

• Context: Began as a housing market problem in the U.S. and escalated into a global financial crisis.
• Impact: Led to a sharp drop in consumer and business confidence, reaching a floor in early 2009. Google search volume for "Great Depression" spiked significantly during late 2008.
• The "Politikmix" (Policy Mix): A coordinated strategy was implemented to overcome the drop in demand.
  • Monetary: The Federal Reserve (Fed) aggressively lowered interest rates.
  • Fiscal: The U.S. government launched a $\$780$ billion investment and tax-cut program.
• Objective: To shift the IS-Curve right and move the interest line down simultaneously to return the economy to its equilibrium growth path.

The 2010 Euro Crisis

• Nature of the Crisis: A combination of an economic crisis, a banking crisis, and a sovereign debt crisis.
• Mechanism: High debt levels for private and public households caused banks to increase the "Risikoprämie" (risk premium) for loans.
• Interest Divergence: The gap between the policy rate ($i^*$) and the market rate ($i$) widened. Even though the ECB lowered the policy rate to the Nullzinslinie (Zero Interest Line), the market interest line remained high or even shifted upward due to risk.
• Liquiditätsfalle (Liquidity Trap): A situation where interest rates are extremely low, but the economy remains in recession because both supply and demand are weak.
• Constraint: A US-style policy mix was impossible for many Eurozone countries because high existing sovereign debt prevented further fiscal expansion (shifting the IS-Curve right).

The Lucas Critique and Practical Limitations

• Disclaimer on Precision: Economic models do not allow for "surgical precision" in steering the economy. Effectiveness depends on numerous real-world factors.
• The Human Factor: Nobel laureate Robert Lucas noted that humans are rational actors who adjust their behavior based on expectations of government policy.
• The Lucas Critique Example: If a government increases spending to boost the IS-Curve, but companies expect this to lead to future tax increases or realize the government has limited long-term funds, they may refrain from investing. In such cases, the intended rightward shift of the IS-Curve fails to materialize as firms don't respond to the stimulus.