Could an economy get stuck on a rational pessimism sunspot path? The case of Japan
研究日本经济是否因理性悲观预期（太阳黑子）陷入长期停滞，发现新凯恩斯模型能解释日本经济行为，并建议财政政策应承诺消除这种悲观预期。
Developed economies have experienced slower growth since the 2008 financial crisis, creating fears of “secular stagnation.” Rational expectations models have forward-looking sunspot solutions, which could cause this; here we investigate the case of Japan. We show that a New Keynesian model with a weak equilibrium growth path driven by pessimism sunspot belief shocks matches Japanese economic behaviour. Another possibility is a conventional model where productivity growth has simply slowed down for unknown reasons. Nevertheless, a welfare-optimising approach implies fiscal policy should commit to eliminating the potential sunspot while being prepared to revert to normal policy if inflation rises. • We develop a model with weak equilibrium growth driven by pessimism sunspot shocks. • Estimated and tested by Indirect Inference to match Japanese economic behaviour. • Welfare optimisation shows fiscal policy should commit to eliminating the sunspot.