Employment Risk, Diversification, and Unemployment
研究1950年以来美国失业率地理分布的成因，发现行业需求协方差结构差异导致各地失业率不同，行业多样化降低失业，且行业结构永久变化带来失业暂时波动。
This paper studies determinants of the geographic distribution of unemployment in the United States since 1950. We argue that "equilibrium" differences in unemployment among markets are partially supported by corresponding differences in the covariance structure of sectoral demands for labor. When workers are mobile, greater diversification of sectoral demands reduces unemployment. We confirm this point using pooled time-series-cross-section data on state unemployment and employment by industry. We also find evidence for nonneutrality of aggregate disturbances based on geographic differences in industrial composition, and that permanent changes in the sectoral composition of employment lead to transitory fluctuations in unemployment.