Envy is cyclical. When things are going well, people are too busy to covet the footwear or summer estates of their compatriots. Then comes the slowdown, and with it the growth of a collective and angry suspicion that money has trumped merit after all and ensconced itself as a new ruling class.

Americans, though, prefer not to give up and wait for the moment to build barricades, as in old Europe. Instead, Americans tend to nurse and use that rage to fuel their personal climb up the economic ladder.

Indeed, individual Americans will even obsess about the scale of social obstacles, just so that they can enjoy the pleasure of proving that they can transcend them.

This American game found its early iteration in Horatio Alger's books of the 19th century. Alger's tales of the rise of "Ragged Dick" and his ill-clad peers sold in the millions.

Every economic downturn, though, brings a fresh Ragged Dick to inspire hope. This season's is Nanny, the heroine of a fiction best-seller, The Nanny Diaries. The authors, Emma McLaughlin and Nicola Kraus, are two former nannies who collected their material on Manhattan's Upper East Side, a fact that gives the book buzz - everyone wonders which witches (the Park Avenue one, or the one who lives on Fifth?) the authors describe. But what has put printings of The Nanny Diaries over the 500,000 mark is that it offers an update on the Horatio Alger message: money threatens merit, yet merit emerges victorious. The sandal-clad young women who serve the pedicured matrons are today's furious strivers.

Consider the plot of The Nanny Diaries. Nanny, the employee, is a deserving education student from "nice" universities (Brown and New York University), clean, bright and very young. Her employer, Mrs X, by contrast lacks every deserving attribute. She is old, in her early forties, mutton sporting the violet Pradas of lamb. She has what are presented in the book (itself quite snobby) as risible education credentials: she attended only the lowly University of Connecticut. She is a Manhattan rich lady, a person universally hated by the rest of America (I'm from Chicago; I know). She is a husband-thief: she supplanted the first Mrs X. And last, she is that greatest of transgressors: a neglectful mother. Or, as the authors put it, the sort of employer who brings in a horde of servants "to collectively provide 24/7 'me time'" for herself; "a woman who neither works nor mothers".

And yet Mrs X is the one with the toile-lined guest bathrooms. And Nanny - her job is her name - is the one so impecunious that she must share a studio apartment with a flight attendant and the attendant's hairy boyfriend. Mrs X subjugates Nanny, forcing her to clean up after her incontinent son and manage hubby's business soirees and requiring her to carry a mobile phone so she will always be available.

Nor is Nanny alone; in fact, there are nannies who face worse inequities. The one genuinely sad moment in this book comes when Nanny encounters an engineer from San Salvador - a woman who, as Nanny notes, "has a higher degree than I will ever receive". Yet because she is an immigrant this woman must babysit and even tolerate the odd body blow from a youngster with a little aggression problem, named Darwin. Money trumps merit, indeed.

And yet from the beginning, as with Horatio Alger's heroes, our Nanny contains within her the seeds of her own victory. As she reminds herself early on, her term as a servant is a limited one: it will end once she graduates and can earn money at a real job. The most tense moment in the book comes when Mrs X nearly hinders her rise by requiring her to work so long one afternoon that Nanny nearly misses her appointment to defend her undergraduate thesis.

In the end, of course, Nanny prevails, walking out and lobbing that emblem of indenture, her mobile phone, into Central Park's reservoir. So confident is she that she leaves with grace, erasing a furious taped message she had prepared for the mistress: "Going to a spa when your son has a fever of 104? News flash: this officially makes you not just a bad person, but like, officially a terrible mother."

And Nanny's fictional rise is neatly paralleled by the authors' new real-life success; as the book jacket reads, "they are no longer nannies".

But The Nanny Diaries also corresponds to a larger American reality. In America obstacles are real. Envy is strong. And money may trump merit. But it does not go on trumping merit for ever. Indeed, as Michael Cox of the Dallas Federal Reserve and Richard Alm pointed out a couple of years ago in Myths of Rich and Poor (Basic Books), Americans move up and down the economic ladder with alacrity. In the 1980s and 1990s, only 5 per cent of those who were in the bottom fifth of the income distribution tables were still in that quintile after 16 years. Four out of five became middle class or better. Minorities shared the gains.

Also interesting is a recent National Bureau of Economic Research paper by Douglas-Holtz Eakin of Syracuse and two others showing that the purest form of striving - starting a business - helps low earners move ahead faster than their peer employees.

In other words, it is not only the plight of the Ivy nanny that is temporary; the plight of the immigrant family can be temporary as well. Although the Hispanic servants in The Nanny Diaries may never earn enough to buy Pradas, their children are likely to be able to afford an au pair - from time to time, at least. It is small wonder our heroine exits the stage feeling optimistic.

For all its limits, America still does better than most nations at offering the sort of the skyline she sees the morning she departs nannydom - one "bathed in pink dawn".

© Copyright 2002 Financial Times