First there were the baby boomers, who begat Generation X, who were succeeded by the millennials, who were born in the early Eighties and in the Nineties.
And now, largely begat by Generation X – or at least those sections of it that didn't grow up to be dinkies (dual income no kids), but may have been yuppies or slackers – has come … well, what exactly?
The race to label the next generation of teenagers began in earnest this week when the television channel MTV proudly announced that it had come up with the term "founders" to denote youngsters born after December 2000.
Founders, MTV assured us, like to stand out from the crowd – in the manner of role models and near contemporaries such as the actress, dancer and "21st Century Girl" singer Willow Smith. And they are called founders, explained MTV president Sean Atkins, because they are going to rebuild systems that have been disrupted: by things such as Facebook and Google, which have reconfigured the news industry.
And by Youtube, which has unsettled the television industry – to the point that the abrasive New York Daily News enjoyed the irony of MTV's "marketing dolts" naming a generation that "no longer pays much mind" to a once revolutionary (to Generation X), but now conventional TV channel.
But isn't this generation-labelling just a load of pop psychology from a pop TV channel, and does it really matter anyway?
According to Dianah Worman, of the Chartered Institute of Personnel and Development, it matters an awful lot and not just to the "marketing dolts". (She doesn't call them dolts. She suggests "they know more about us than we know about ourselves".)
Ms Worman, the author of the report "Gen Up", about how generations interact in the workplace, says that appreciating "generational diversity" is a vital skill for all manner of businesses – and for life in general.
"Businesses, and certainly the leading edge players, are starting to take this increasingly seriously," she says. "It fits into the way you recruit and retain the best talent, how you behave towards customers and clients, and the way we engage with human beings. You do that better if you understand them."
And nor is "generational theory" just psychobabble. Dr Graeme Codrington, the co-author of Mind the Gap, a book exploring generational differences, has suggested that elements of generational theory can be traced to at least the 14th century, when the Bedouin scholar Ibn Khaldun devised his cyclical theory of generational fortunes.
The first generation rises thanks to its desert toughness, the second enjoys the resulting rewards of luxury and power but retains a sense of the old virtues thanks to direct contact with the elders. The third lot are just decadent. Decline sets in.
Dr Codrington has also suggested that in the early 20th century the sociologist Karl Mannheim helped to make generational theory a respectable academic subject. While young people did learn values from their parents' generation, wrote Mannheim, their different experiences of society produced a "visible and striking transformation of the consciousness". So each generation acquired its own "collective mentality".
But for all the academic pedigree, no-one was suggesting generational labels could be applied with wild abandon.
For one thing, you had to look out for "cuspers", people who fall into the overlap between two generations – people such as David Cameron, born 1966, on the cusp between the baby boomers and Generation X.
Dr Codrington has written that their dual status makes cuspers "great generational mediators [which] makes them extremely valuable in multi-generational workplaces." Perhaps that's why Mr Cameron is having slightly less problem with party unity than out-and-out baby boomer Jeremy Corbyn (born 1949).
The theorists of MTV and their followers should also beware of "ethnographic dazzle", a term coined by the anthropologist Robin Fox to describe how surface differences blind us to our basic human similarities.
And if applied crudely, says Ms Worman, generational labels could provoke a "stereotype threat" reaction, "because none of us likes to be labelled. We want to be treated as the individuals we are."
Although at least one "founder" questioned by Time magazine didn't seem to mind MTV's label that much. "Considering the other names out there," said Griffin Picciani, 14, "it's a lot easier to remember."
Which seems more Generation X slacker than founder.
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