For the first time, middle-aged men and women are the largest, most influential, and richest segment in the country. Floating somewhere between 40 and 64, they constitute one-third of the population and control nearly seventy percent of its net worth. In booms and recessions, a trillion-dollar economy feeds and fuels their needs, whims, and desires. Better-educated and healthier than their predecessors, these early and late midlifers are happier, more productive, and more involved than any other age group. Women are part of the first generation to enter their 40s and 50s after the feminist movement, and they have options that their mothers and grandmothers could barely imagine. […]