Dent proposed that economic boom and bust times are determined by demographic factors.
Individual spending tends to peak in the mid-forties.
Thus, aggregate spending should correlate with the size of the mid-forties population. If we plot the estimated size of the mid-forties age cohort with year we obtain a generally rising trend that shows a number of peaks and troughs due to past variations in birth and immigration rates. For example fewer babies were born during the Great Depression and World War II than either before or afterward. Dent proposes that economic boom times are associated with increasing size of the mid-forties population and that bust times are associated with a decreasing size of this population. In his book, Dent shows a graph that shows a close correlation between the Standard and Poor 500 index in constant dollars and the birth rate 44-46 years in the past.