Who are our MPs? I became interested in the question after I read Dave's post about Disraeli and his blue-collar Toryism, and wondered how many blue-collar MPs there are. Thanks to the House of Commons Library, it proved easy to plot trends in MPs' backgrounds over the past 30 years, and work out what they did before arriving in Westminster.

It's an interesting picture. The proportion of Parliamentarians coming from manual occupations, for example, has steadily declined. Compare that to the rise in white-collar backgrounds:

Across all elections and through successive governments, that's a pretty clear trend. The label 'white-collar' is quite catch-all, but the data distinguishes between this miscellaneous category, and the traditional professions - barristers, doctors, accountants, teachers and so on. The pattern for this larger group is equally interesting - especially when plotted against the percentage of MPs who previously worked in, er, politics...

Again, some clear trends - a steady rise of the political operative, as professionals see a gradual dip in numbers. There might be some complicating factors here: in 2010, 20% of new Labour MPs had a political background, compared to 10% of Conservative and 12% of Lib Dems. That might be the consequence of a long period of Government, with unusually high numbers of former advisers and staffers finding seats. Equally, in 2010 the proportion of MPs with business backgrounds grew from 19.2% to 25.2%, mostly thanks to new Tory MPs - 20 new Labour MPs came from business, compared to 125 Tories - so it's not all about decreasing levels of real-world experience.

Still, the overall pattern is clear and largely consistent from the early 1980s: fewer former professionals, and more former politicos.

One final graph can show us two individual career types - farmers and miners.

Now, it might look odd to graph these two specific occupations. But in their own way, they each represent a shade of postwar Britain - old agriculture and old industry. Both had their heyday. Neither exists in substantive political form any more; and just as we're a generally urban, post-industrial country, fewer MPs now come from farming or mining backgrounds. In this sense, Parliament reflects the bigger societal change. Perhaps the same can be said for the decline of MPs from manual occupations - it might have something to do with the UK having far fewer skilled trade jobs than it did 30 years ago.

So you can argue that the Commons is a mirror of the nation, and its composition can tell us something about the state of wider British society.

If that's the case, we should worry about these numbers. They suggest our MPs are largely drawn from a small and shrinking pool. They are middle-class, and increasingly are political class.

This is not the hallmark of a healthy, representative political culture.

This article was originally published on platform10.org