This volume brings together and expands on a body of research that I began in the early 1960s and have continued up to the present. It deals mainly with shiftwork-work that is performed during other than normal daytime hours. Shiftwork is a characteristic of economic life in the United States and abroad that has increased in importance over the years; according to the Bureau of Labor Statistics, one out of five full-time and part-time employees in the United States works on shifts. My interest in this field concerns fixed capital, specifically, changes in weekly hours worked by capital over long periods of time, and the signifi­ cance of those changes in the measurement oflong-run productivity change. In studies of growth, the measurement of capital input-by capital stocks or the services yielded by those stocks-typically makes no allowance for the changing hours worked by capital. Capital services are assumed to be propor­ tional to the stocks. Consequently, in analyses of output growth in a growth­ accounting framework, the effect of longer capital hours is a component of multifactor or total factor productivity growth.