The “demography and destiny” theme refers to the way changes in demographic variables such as fertility and mortality transform the circumstances facing individuals, thereby altering the nation’s social and economic course. Family size and Iife expectancy are two of the variables whose consequences we will examine in detail. The timing of birth is also important: men and women who reached adulthood during the Great Depression made decisions very different from those of youth who entered adulthood during World War II or the peacetime prosperity of the 1950s. Economist Richard Easterlin (1980) has emphasized that even variations in the number of young people reaching maturity can result in systematic differences in life cycle behavior,
The theme of “wanting and waiting” concerns the importance of delay of gratification, or time discount, in shaping the way we live, Almost every choice discussed in this book, whether pertaining to fertility, schooling, health, occupation, or other areas of life, involves comparisons between present and future costs and benefits. The willingness and ability of individuals to invest in the future, to forgo present wants and to wait for future benefits, have major consequences for their own lives, for the lives of their children, and for society as a whole.