Microtrends, By Mark J Penn with E Kinney Zalesne

Like many men who announce themselves with a middle initial, Mark J Penn can hardly be said to suffer from a surfeit of humility. Within the first few pages of Microtrends, he tells us he has been to Harvard, that he helped Bill Clinton to success in the 1996 Presidential election, that Bill Gates is a fan of his and that he has even done some work for Tony Blair. Too grand to write a book all on his own, Penn has worked on it "with" a colleague. Modesty might not be his strong suit, but if you can forgive him his entrepreneurial swagger, there's a fascinating book ready to leap out.

Among demographers and policy wonks, Penn is chiefly famous for having noticed an emerging demographic of so-called "Soccer Moms", a group of US mothers who had not yet made up their mind how to vote in the 1996 election, and whom Penn saw could be made susceptible to Clinton's charms. The reason why he settled on the title of Microtrends was that "the one-size-fits-all approach to the world is dead". As if to prove that point, Penn abjures any overriding narrative thread in favour of 75 gobbets of mini-argument – the microtrends that he argues are quietly shaping society, and nudging their way into what remains of the mainstream.

Much of what Penn has to tell us is hardly novel, but worth repeating. Single living is on the up, changing not only how we spend money but the constitution of our inner cities. So are office romances, as more people spend more time at work. More people are working beyond 65, not only because they have to, but because otherwise they would get bored. At least in America, internet dating has become socially respectable.

Some of Penn's microtrends, however, are a little more ritzy. Once the preserve of middle-aged frumps, knitting is now the height of chic among young people, who see it as therapy and a nice way to escape from new technology. Women, at least in North America, are on the verge of taking over "word-based professions" like journalism, law, marketing and communications. The average age of American computer game players is now 33, up from 24 in just four years. While Penn's focus is on the US, it is testament to the small world we now live in that almost all his trends have global significance.

Much of the considerable fun of Microtrends derives from the way in which Penn wraps a slight statistical blip around a gimmicky buzzword. On discovering that the average American now sleeps less than seven hours a night, a drop of about 25 per cent since the early 1900s, he finds room for a whole new demographic of "30 Winkers". "Late-breaking gays" are gay people who have come out belatedly because of greater social acceptance of homosexuality, which accounts for all those touching public speeches by American politicians discovered spending too much time near public toilets.

Long-term monogamous couples who "live apart together" in different residences are dubbed "LAT's". With a million couples living this way, this is one of the few social innovations in which Britain can count itself as world leader.

Occasionally, Penn's statistical eureka moments come perilously close to parody. The travails of Russian democracy are filed under the label of "Russian swings", as if the idea of the "swing voter" beloved by Western psephologists could explain Russia's lurch towards authoritarianism. On discovering that a disproportionately high number of American black women are fatties, Penn knows exactly how to write it up: "Big Momma's heartache."

If there is an overarching thesis, it is that society has exploded into "hundreds of small niches" which all require the careful attention of demographers, marketers and politicians. It is an endlessly fascinating hypothesis, which echoes far and wide – from television to sport, even religion.

While some jeremiahs think we are shaping up for a tripartite battle between Christianity, Islam and the guardians of Enlightenment, it would be more accurate, Penn argues very perceptively, to say that mainstream religions have fragmented into thousands of different sub-groups. The resulting tensions between each of those groups fuel violence, conflict and alienation.

Politics, too, is crumbling under the weight of social disaggregation. Both major political parties in the US have become fragile and fleeting coalitions. Penn knows this because he is Hillary Clinton's chief strategist, already poised to mop up as many of these myriad little constituencies as he can. The same changes which have shaped US politics, however, are quietly shaping the British system. Both Gordon Brown and David Cameron, just like Blair before them, come armed with their own self-styled polling geniuses, just waiting in the wings to slice and dice us all into demographics manageable enough to court with a policy gimmick or an ingratiating speech. Inspiring news for political entrepreneurs in search of a new campaign, but depressing for anyone who hopes to be argued with as a citizen rather than flattered as an off-the-peg demographic buzzword.

James Harkin's 'Big Ideas: the essential guide to the latest thinking' will be published by Atlantic in February

Allen Lane £20 (345pp) £18 (free p&p) from 0870 079 8897