I develop an idea flows theory of firm and worker dynamics in order to assess the consequences of population aging. Older people are less likely to attempt entrepreneurship and switch employers because they have found better jobs. Consequently, aging reduces entry and worker mobility through a composition effect. In equilibrium, the lower entry rate implies fewer new, better job opportunities for workers, while the better matched labor market dissuades job creation and entry. Aging accounts for a large share of substantial declines in firm and worker dynamics since the 1980s, primarily due to equilibrium forces. Cross-state evidence supports these predictions.

This appendix contains eight sections. Section 1 gives technical details of how we calculate standard errors in the CPS data. Section 2 discusses changes in the ACS procedures before 2005. Section 3 examines demographic and economic patterns in migration over the past two decades, in more detail than in the main paper. Section 4 examines the cross-sectional variance of location-occupation interactions in earnings when we define locations by MSAs instead of states. Section 5 describes alternative methods to estimate the variance of location-occupation interactions in income. Section 6 measures the segregation of industries across states and of occupations and industries across MSAs. Section 7 gives technical details on the use of SIPP and census data to calculate repeat and return migration rates. Section 8 discusses transition dynamics in the model.

We analyze the secular decline in interstate migration in the United States between 1991 and 2011. Gross flows of people across states are about 10 times larger than net flows, yet have declined by around 50 percent over the past 20 years. We argue that the fall in migration is due to a decline in the geographic specificity of returns to occupations, together with an increase in workers’ ability to learn about other locations before moving there, through information technology and inexpensive travel. These explanations find support in micro data on the distribution of earnings and occupations across space and on rates of repeat migration. Other explanations, including compositional changes, regional changes, and the rise in real incomes, do not fit the data. We develop a model to formalize the geographic-specificity and information mechanisms and show that a calibrated version is consistent with cross-sectional and time-series patterns of migration, occupations, and incomes. Our mechanisms can explain at least one-third and possibly all of the decline in gross migration since 1991.

We show that much of the recent reported decrease in interstate migration is a statistical artifact. Before 2006, the Census Bureau's imputation procedure for dealing with missing data inflated the estimated interstate migration rate. An undocumented change in the procedure corrected the problem starting in 2006, thus reducing the estimated migration rate. The change in imputation procedures explains 90 percent of the reported decrease in interstate migration between 2005 and 2006, and 42 percent of the decrease between 2000 (the recent high-water mark) and 2010. After we remove the effect of the change in procedures, we find that the annual interstate migration rate follows a smooth downward trend from 1996 to 2010. Contrary to popular belief, the 2007–2009 recession is not associated with any additional decrease in interstate migration relative to trend.

This paper proposes a new way of modeling age, period, and cohort effects that improves substantively and methodologically on the conventional linear model. The linear model suffers from a well-known identification problem: If we assume an outcome of interest depends on the sum of an age effect, a period effect, and a cohort effect, then it is impossible to distinguish these three separate effects because, for any individual, birth year = current year – age. Less well appreciated is that the model also suffers from a conceptual problem: It assumes that the influence of age is the same in all time periods, the influence of present conditions is the same for people of all ages, and cohorts do not change over time. We argue that in many applications, these assumptions fail. We propose a more general model in which age profiles can change over time and period effects can have different influences on people of different ages. Our model defines cohort effects as an accumulation of age-by-period interactions. Although a long-standing literature on theories of social change conceptualizes cohort effects in exactly this way, we are the first to show how to statistically model this more complex form of cohort effects. We show that the additive model is a special case of our model and that, except in special cases, the parameters of the more general model are identified. We apply our model to analyze changes in age-specific mortality rates in Sweden over the past 150 years. Our model fits the data dramatically better than the additive model. The estimates show that the rate of increase of mortality with age among adults became more steep from 1881 to 1941, but since then the rate of increase has been roughly constant. The estimates also allow us to test whether early-life conditions have lasting impacts on mortality, as under the cohort morbidity phenotype hypothesis. The results give limited support to this hypothesis: The impact of early-life conditions lasts for several years but is unlikely to reach all the way to old age.

We investigate the consequences of demographic change for business cycle analysis. We find that changes in the age composition of the labor force account for a significant fraction of the variation in business cycle volatility observed in the U.S. and other G7 economies. During the postwar period, these countries experienced dramatic demographic change, although details regarding extent and timing differ from place to place. Using panel-data methods, we exploit this variation to show that the age composition of the workforce has a large and statistically significant effect on cyclical volatility. We conclude by relating these findings to the recent decline in U.S. business cycle volatility. Using both simple accounting exercises and a quantitative general equilibrium model, we find that demographic change accounts for a significant part of this moderation.

We develop and calibrate an overlapping generations general equilibrium model of the U.S. economy with heterogeneous consumers who face idiosyncratic earnings and health risk to study the implications of exogenous trends in increasing college attainment, decreasing fertility, and increasing longevity between 2005 and 2100. While all three trends contribute to a higher old age dependency ratio, increasing college attainment has different macroeconomic implications because it increases labor productivity. Decreasing fertility and increasing longevity require the government to increase the average labor tax rate from 32.0 to 44.4 percent. Increasing college attainment lowers the required tax increase by 10.1 percentage points. The required tax increase is higher under general equilibrium than in a small open economy with a constant interest rate because the reduction in the interest rate lowers capital income tax revenues.