Although much of its current popularity can be traced to the influential 1991 book “Generations” by Neil Howe and William Strauss, generational thinking dates back to the second half of the 19th century. Sarah Laskow of The Atlantic explained in 2014 that philosophers at this time were, in the words of the sociologist Karl Mannheim, “anxious to find a general law to express the rhythm of historical development, based on the biological law of the limited lifetimes of man.” /But understanding societal phenomena through the lens of groups of people born around the same time has always had its limits.

For example, it’s true that for young men coming-of-age during the Vietnam War, being born in a particular year (and, thanks to the draft lottery, on a particular day) could be life-shaping. But even here, an individual’s class was a factor in whether he actually went to war — men from privileged backgrounds had many options to avoid the draft, the burden of which fell mainly on the working class.

Like war service, entering the labor market at a time of recession, as most millennials did, can be difficult. But race and class are more important in affecting how this experience plays out for individuals.

Take white millennial college graduates: Yes, they’re part of an age cohort that has experienced worse economic conditions than graduates of the preceding generation — but that doesn’t give us a particularly meaningful understanding of their plight, given that they are still better off when it comes to income than the average non-college-educated worker of any age.

Some may argue that the generation game, if intellectually vacuous, is basically harmless. But dividing society by generation obscures the real and enduring lines of race, class and gender. When, for example, baby boomers are blamed for “ruining America,” the argument lumps together Donald Trump and a 60-year-old black woman who works for minimum wage cleaning one of his hotels.

The pattern of inherited privilege points to yet another reality that the generation game ignores: the decline of social mobility between generations and the rise of what the French economist Thomas Piketty has called a “patrimonial society.” When it comes to wealth and its accompanying privileges, the wealth of the previous generation of one’s own family matter more than whether your birth year falls on one or other side of some arbitrary boundary.

Today’s young people may choose political action aimed at reversing these trends or to let them continue and accelerate. But their choices will be determined by their political judgments and personal commitments, not by a number on a birth certificate.