The poverty line is a stock figure of American statistical and political culture. Most of us are at least dimly aware that it is an official level of income used to separate the poor from the non-poor, that the government somehow sets it, that it changes from time to time, and that it is the topic of periodic political fights. Even those who know its arcane details, however, usually forget that our official measure of poverty was once crafted by a real person with a passion and a pencil.

Once when I was about nine, I wandered into my aunt's kitchen during Thanksgiving to find all the grown-up women whispering, hugging, and crying. When they explained to me what was going on (Auntie Cookie had just found out she was going to have another baby and they were crying from happiness), they confirmed a story I already knew--the one about how babies just happen, and women to whom they happen are considered very lucky. How else to explain the crying? A few years later, when my friend Phyllis told me her parents were "trying to make" another baby, I had the crashing revelation that human actions create babies.