Today, the time span of a generational cohort is usually taken to be around fifteen years (even though the median age of first-time mothers in the U.S. is now twenty-six and of first-time fathers thirty-one). People born within that period are supposed to carry a basket of characteristics that differentiate them from people born earlier or later.
This supposition requires leaps of faith. For one thing, there is no empirical basis for claiming that differences within a generation are smaller than differences between generations. (Do you have less in common with your parents than with people you have never met who happen to have been born a few years before or after you?) The theory also seems to require that a person born in 1965, the first year of Generation X, must have different values, tastes, and life experiences from a person born in 1964, the last year of the baby-boom generation (1946-64). And that someone born in the last birth year of Gen X, 1980, has more in common with someone born in 1965 or 1970 than with someone born in 1981 or 1990.
Everyone realizes that precision dating of this kind is silly, but although we know that chronological boundaries can blur a bit, we still imagine generational differences to be bright-line distinctions. People talk as though there were a unique DNA for Gen X—what in the nineteenth century was called a generational “entelechy”—even though the difference between a baby boomer and a Gen X-er is about as meaningful as the difference between a Leo and a Virgo.
You could say the same things about decades, of course. A year is, like a biological generation, a measurable thing, the time it takes the Earth to orbit the sun. But there is nothing in nature that corresponds to a decade—or a century, or a millennium. Those are terms of convenience, determined by the fact that we have ten fingers.
Yet we happily generalize about “the fifties” and “the sixties” as having dramatically distinct, well, entelechies. Decade-thinking is deeply embedded. For most of us, “She’s a seventies person” carries a lot more specific information than “She’s Gen X.” By this light, generations are just a novel way of slicing up the space-time continuum, no more arbitrary, and possibly a little less, than decades and centuries. The question, therefore, is not “Are generations real?” The question is “Are they a helpful way to understand anything?”
Bobby Duffy, the author of “The Generation Myth” (Basic), says yes, but they’re not as helpful as people think. Duffy is a social scientist at King’s College London. His argument is that generations are just one of three factors that explain changes in attitudes, beliefs, and behaviors. The others are historical events and “life-cycle effects,” that is, how people change as they age. His book illustrates, with a somewhat overwhelming array of graphs and statistics, how events and aging interact with birth cohort to explain differences in racial attitudes, happiness, suicide rates, political affiliations—you name it, for he thinks that his three factors explain everything.