The growth rate of national income has fluctuated widely in the United States since 1929. In this volume, Edward F. Denison uses the growth accounting methodology he pioneered and refined in earlier studies to track changes in the trend of output and its determinants. At every step he systematically distinguishes changes in the economy’s ability to produce—as measured by his series on potential national income—from changes in the ratio of actual output to potential output. Using data for earlier years as a backdrop, Denison focuses on the dramatic decline in the growth of potential national income that started in 1974 and was further accentuated beginning in 1980, and on the pronounced decline from business cycle to business cycle in the average ratio of actual to potential output, a slide under way since 1969. The decline in growth rates has been especially pronounced in national income per person employed and other productivity measures as growth of total output has slowed despite a sharp acceleration in growth of employment and total hours at work. Denison organizes his discussion around eight table that divide 1929-82 into three long periods (the last, 1973-82) and seven shorter periods (the most recent, 1973-79 and 1979-82). These tables provide estimates of the sources of growth for eight output measures in each period. Denison stresses that the 1973-82 period of slow growth in unfinished. He observes no improvement in the productivity trend, only a weak cyclical recovery from a 1982 low. Sources-of-growth tables isolate the contributions made to growth between “input” and “output per unit of input.” Even so, it is not possible to quantify separately the contribution of all determinants, and Denison evaluates qualitatively the effects of other developments on the productivity slowdown.