期刊-NBER美国国民经济研究局-2017number3_40页_2mb

NBER Reporter Summary - September 2017

Core Content

This issue of the NBER Reporter includes a lecture by Mervyn King titled "Uncertainty and Large Swings in Activity", delivered at the 40th NBER Summer Institute. The article discusses the limitations of traditional macroeconomic models in explaining recent economic phenomena, particularly the slow recovery from the 2008–09 financial crisis and the decline in real interest rates. It also explores the concept of radical uncertainty and its implications for economic analysis and policy-making.

Main Points

Mervyn King's Lecture

• Focus: King reflects on the evolution of macroeconomic thought, from microeconomics to macroeconomics, and discusses the inadequacy of the canonical one-sector models in capturing the complexities of modern economic activity.
• Key Themes:
  • Uncertainty and Stochastic Shocks: Traditional models assume that economic activity fluctuates around a stationary long-run equilibrium due to stochastic shocks. However, the data suggests that such shocks are not stationary, and the economy has experienced significant, non-repeating deviations.
  • Limitations of Expected Utility Theory: King argues that expected utility theory, which underpins many macroeconomic models, is unsuitable for analyzing large swings in economic activity due to its reliance on Bayesian reasoning and subjective probabilities.
  • Radical Uncertainty: He emphasizes the importance of recognizing radical uncertainty, where we cannot enumerate all possible states of the world or assign probabilities to them. This challenges the assumption of stationarity in economic models.
  • Narratives and Decision-Making: King suggests that in the face of radical uncertainty, individuals and policymakers rely on narratives rather than probabilistic models to make decisions. These narratives help integrate key information and guide judgment.

The One-Sector Model

• Dominance: One-sector Dynamic Stochastic General Equilibrium (DSGE) models have dominated macroeconomic teaching and policy.
• Limitations:
  • These models assume forward-looking agents who optimize over known probability distributions.
  • They fail to account for the non-stationarity of economic shocks and the composition of aggregate demand, not just its level.
  • They are ill-suited to explain the slow growth and current account imbalances observed in recent decades.

The Two-Sector Model

• Introduction: King proposes a two-sector model that distinguishes between tradable and non-tradable goods and services.
• Key Insights:
  • The turnpike theorem suggests that economies should move toward and stay close to a balanced growth path.
  • The reallocation of resources between sectors is crucial for long-term stability.
  • The relative price ratio of tradables to non-tradables has been a key factor in economic imbalances.
• Rebalancing: The need for rebalancing in the wake of the financial crisis is highlighted, with a focus on the real exchange rate and its impact on current account deficits.

Key Information

• NBER Overview: The National Bureau of Economic Research is a private, nonprofit research organization founded in 1920, focused on objective quantitative analysis of the American economy.
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Figures and Data

• Figure 1: GDP per capita for the U.S. and U.K. from 1900 to 2016 shows a steady growth path with major deviations during the Great Depression and WWII.
• Figure 2: Distribution of deviations from the U.S. GDP trend indicates non-normality and suggests non-stationarity.
• Figure 3: World real interest rates have declined significantly since the 1980s, challenging the one-sector model.
• Figure 4: Gross national saving rates for China and Germany show a marked increase, while the U.S. and U.K. have seen a decline.
• Figure 5: Saving rates in the U.S. and U.K. from 1980 to 2016 indicate a shift in economic behavior.
• Figure 6: Illustrates the optimal path for a two-sector economy, showing the movement toward a balanced growth path.
• Figure 7: Relative price ratio of tradables to non-tradables in the U.K. and Germany from 1996 to 2014 highlights the imbalance in the economy.

Conclusion

King advocates for moving beyond the one-sector canonical model to a more nuanced two-sector framework that accounts for the composition of aggregate demand and the reallocation of resources. He also emphasizes the importance of radical uncertainty and the need to incorporate narratives and non-stationary assumptions into macroeconomic analysis and policy-making. The lecture serves as a call for more flexible and realistic models that can better explain the complexities of the modern economy.