This research explores how changes in the relative sizes of different age cohorts affect older workers’ employment. It is prompted by the question: Does the relative scarcity of younger workers boost demand for older workers? Evidence on how employment of older individuals is affected by a relative scarcity, or abundance, of younger workers in more recent cohorts can lead to more reliable long-term predictions of employment and labor force participation rates of older cohorts. The project will use long-term data on cohort size and cohort employment and labor force participation rates over many decades, exploiting variation across states in a panel-data setting. Because of distinct migration patterns of those near and past usual retirement ages, historical data by state and cohort will be used as an exogenous source of variation in states’ current demographic structures in an instrumental variables framework.