Foreigners can find Britain's class system baffling and fascinating. With its traditional divisions declared obsolete by sociologists, an American offers his take on the new seven-tier model.

The BBC's Great British Class survey has pretty much killed productivity at my end of Facebook. Everyone in my network is taking it and laughing out loud at the results (read to the bottom and I'll tell you what class I'm in).

But beyond starting a light-hearted national conversation on what class in Britain is today, BBC Lab UK's attempt to redefine class boundaries in UK society is a worthy idea.

I spend a lot of time thinking about it - particularly since the onset of the recession - when my "class-ification" took a severe knock. Pretty clearly, it is well past time for a redefinition of terms.

When I spent a junior year abroad at Oxford University in the 1970s, social class was defined by your origin, despite the faux egalitarianism of the time.

Image caption Oxford students would delight in mocking others over their backgrounds

Those origins had a long history. All sides played Spot the Fake Accent: whether it was the grammar school boy mocking the toff playing at being one of the ordinary lads, or the first generation middle-class kid being satirised for trying to sound posh.

But as with so much else in British society, a great change began during Margaret Thatcher's time in office.

The Great British class calculator The original survey contained more than 140 questions and covered wealth, recreation and social networks

See where you fit in the new model

Find out how Britain is segmented Use the calculator Explore more BBC citizen science discoveries

She either - depending on your politics - "tamed the unions" or "made war on the unions". Either way, she caused an earthquake within the traditional working class.

Thatcher became the patron saint of working-class strivers (as they would now be called) by giving council tenants the right to buy their homes. Anyone, regardless of background, could buy shares in the flotation of previously nationalised industries. A property-owning, shareholding society - and open to all - was her vision. "Tell Sid" was the ad slogan for British Gas shares, not "Tell Rupert" or "Tell his Lordship".

Money, which had really not featured in the British demarcation of social class, became very important. This was a huge change. Comics and satirists had a field day creating characters like Harry Enfield's Loadsamoney. Caryl Churchill won major awards on both sides of the Atlantic with her play Serious Money, in which the "oiks" in the City of London take over from the gents.

This was around the time I moved to Britain permanently from the US.

Interestingly, even as Thatcher was working to open things up and making the British class system more like America's, the US class system started becoming more and more rigid.

Image caption The Right to Buy policy turned working class families into homeowners

Today, one of the few things US politicians on the right and the left agree on is social mobility in their country has calcified. It is actually lower than in Britain, as the New York Times noted last year.

Why it took so long to figure this out is beyond me. It's been clear since the 1970s that the class system was becoming more inflexible.

The great upthrust of the immigrant working class into the middle class after World War II, via the GI Bill, was stopped stone cold by the events of the autumn of 1973, when the October war in the Middle East led to the quadrupling of oil prices virtually overnight and the great inflation set in.

Personal testimony: my father was a clinical professor at a Philadelphia medical school. He made a very nice living. Like seeks like, and we lived in a neighbourhood of doctors, lawyers, executives, stockbrokers and successful entrepreneurs. You had to work hard to fall out of that class.

Plenty of my school fellows did just OK in high school, went to second-rank universities, where they majored in having a good time, crammed for the LSAT (law school test) and squeezed into second-rank law schools or business schools.

They emerged on the other side with a credential that allowed them to make a pretty good living without putting themselves out too much. A young man from an inner-city school in Philadelphia who took the same relaxed approach to study and career would never have made it to law school or business school.

It was entirely likely that young man had brushes with the law and possibly ended up in prison, as a look at incarceration rates for 18- to 25-year-old African American males in the 70s and 80s will confirm. And if you were white and working class, listen to the songs of Bruce Springsteen to get a sense of the frustrations.

Image caption What will get you into Harvard?

What was true almost 40 years ago is even more true today. As many as 15% of white students admitted to elite colleges don't meet admissions standards. They do meet a more important requirement - their parents are alumni or big donors, according to the Boston Globe.

In Britain we call this the class system at work. But it still leaves the work of redefining social class.

More US views on class in Britain US historian Dr Tim Stanley summed up the difference between social status in the US and UK for the Daily Telegraph: "To Americans, social status is all about money and power. To Brits it is all about birth and accent." Slate says American concern about inequality is soothed by Downton Abbey: "There is in the show's popularity some quality of nostalgia for a class structure we never had. We don't wholly approve of it... but are somehow entranced." The Atlantic notes: "The calculator is distinctly British. Part of the questionnaire, for example, asks if you regularly 'go to stately homes'. Answering yes instantly increases your cultural capital."

The problem is how do you factor in money. What does it measure in terms of class? Should it be the sole arbiter of class? And if it is, what do mega-events like the crash of 2008 do to the class structure?

Anyway, if you've read this far you would probably peg me as upper middle class, kind of privileged. My CV would verify that impression, yet, according to the BBC survey, I am a member of the "precariat". Well, no kidding. I'm a freelance journalist.

Although once upon a time I had a staff job with all the appurtenances. Had I filled out the questionnaire seven years ago, I would have been categorised as either "established middle class" or "new affluent" because back then I could afford to go to the theatre regularly and went to dinner at posh restaurants.

I had a much wider circle of acquaintances. If you can't go out to the pub, or if you're feeling low because money is so tight, you just lose touch with people. Going out, a wide circle of acquaintances - cultural capital and social capital - are key factors in determining your social class, according to the survey.

Instead, I am in the "precariat", which means I am likely to come from a working class background. No, I don't, although I suppose my daughter will be typed that way. Mind you, I don't feel alone on my downwardly mobile path. On both sides of the Atlantic, I know plenty of people who are in my position - successful wage earners thrown out of work for the apostasy of turning 50. Today we work as freelancers or consultants. It's a fast growing category, according to the New York Times.

Are we still middle class? Probably. So are there three social classes or seven or 100?

Maybe, given the uncertainty of the contemporary economy, we should keep everything fluid and paraphrase Supreme Court Justice Potter Stewart's definition of obscenity by saying when it comes to define middle class, working class, upper class or precariat class: "I know it when I see it."

Michael Goldfarb is a former London bureau chief for National Public Radio.

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