identity of individual respondents is known. The Census databases include consistent data over a long period of time but cannot collect every question. Combining them with data in commercial databases or collected by researchers would increase the power of both data sets. For example, CES has teamed up with researchers at Carnegie Mellon to look at the impact of managed care on innovation in health care, which will link bibliometric and patent information with economic data on firms and hospitals. CES is also exploring with the American Medical Association (AMA) the possibility of linking AMA data on education and specialization of physicians with economic census information to study doctors’ offices.
Jensen discussed one limitation on the Census economic data. Census does not survey very small establishments with less than 20 employees; it relies on administrative data from the Internal Revenue Service to capture some employment and payroll information on them. This reflects the primary focus of the Census Bureau on developing an accurate picture of aggregate economic activity as an input to the national product accounts of the Bureau of Economic Analysis. Very small establishments account for little economic activity. Nevertheless, this makes it harder to study business start-ups and to understand under what circumstances start-ups become large enough to join Census’ sample frame. There are also problems in tracking mergers and acquisitions among small firms, because the amount of financial assets that changes hands may be trivial compared with the exchange of human capital, which is not measured. This is an issue that might be addressed by using human resources data to track the movement of innovative activity.
Julia Lane, Professor of Economics at American University, described the Longitudinal Employer Household Dynamics Project at the Census Bureau, a collaboration with John Abowd, Cornell University, and John Haltiwanger, University of Maryland. They are using administrative data from the Social Security Administration as the link record between information about individual persons, including earnings and employment histories, and economic data collected about their employers. With respect to scientists and engineers or highly educated individuals generally, because there are repeated observations on individuals, a relatively small initial sample frame becomes a much larger one. One could examine both cohort and temporal effects and career mobility.