Eighteen years later, the political battle for the centre ground was won by Labour, again with a carefully targeted appeal to what the popular press dubbed ‘Sierra Man’.

Today the concept of the ‘middle’ is extensively used, but often in contradictory ways. Mostly it has been used as shorthand for the middle class, a group with earnings that take them well into the top half of the income distribution. In one report, Middle Britain in 2008, published by insurance company AXA, the group was defined, without irony, as those households that ‘typically earn gross household incomes of between £40,000-£100,000, and have an average income of £62,000′. When the coalition government axed child benefit for families on incomes above the higher rate tax threshold, it was, according to much of the press, middle Britain that would suffer.

Although political parties claim they are talking of ‘the very heartland of the nation’, the term is sufficiently elastic that a quite different set of values has been ascribed to the same group. In the run-up to the 1997 election, Labour talked of the middle as a ‘constituency of enlightened self-interest, perhaps even altruism, where voters would happily pay more taxes for better schools and hospitals’. For Conservatives, middle Britons preferred ‘tax cuts and for people to stand on their own two feet’.

So is there a less elastic way of defining the middle? The most objective measure is its position in the income distribution, though this leaves two alternative ways of defining the centre. First, the ‘mean’, calculated by dividing the total incomes in the country by the number of people. It is this measure that is often implicitly used by commentators when they talk and write about middle Britain. But despite its widespread use, the mean is a poor measure of the middle. The alternative is the ‘median’, the income level that divides the population in two when individuals are ranked by income. As the median income is literally the level enjoyed by the ‘middle person’ – half the population falls below and half above – it is arguably a superior definition of where the centre actually lies. Indeed, it is the median, not the mean, that is used by the government to measure the level of poverty.

If incomes were evenly distributed (corresponding to what statisticians refer to as a ‘normal distribution’, one which takes the shape of a bell curve) the median and mean income would be the same, coinciding in the centre of the distribution. In 1980, the income distribution was closer to a bell shape than it is today. In that year, the mean income was seven per cent higher than the median. Since then, the gap has widened sharply. In 2008-9, the mean net household income after tax stood at £507 per week, a quarter more than the median income of £407.

What this shows is that those on middle incomes have been performing much more poorly than those on higher incomes. In effect, the bottom half of the distribution has been sinking, with a much larger proportion of the population bunched at the bottom. Indeed, close to two-thirds of households live on incomes that are below the mean. This is because the gains in prosperity over the last three decades have been very unevenly shared. Between 1978 and 2008, while realearnings at the 90th percentile (the point exceeded by 10 per cent of earners)doubled, real median earnings rose by only 56 per cent while real earnings at the 10th percentile by a mere 27 per cent.

So just who are the ‘squeezed middle’? A YouGov survey for the TUC carried out in 2009 found that middle-income households are concentrated among socioeconomic groups C1 and C2 – a mix of white collar and skilled manual workers. The men typically work as customer service administrators, debt collectors, despatch clerks, retail managers, HGV drivers, IT workers, joiners, landscape gardeners. The women are clerical and administrative workers, teaching assistants, care coordinators, caterers, librarians and shop assistants.

This group is more likely to have experienced unemployment, less likely to enjoy a final salary pension scheme and much less likely to hold shares and have significant levels of savings compared with those further up the income hierarchy.

The survey found that, although many in the ‘squeezed middle’ acknowledge they have moved up a class compared with their parents, working in white collar rather than skilled manual jobs, this has not brought a rise in status or in relative wages. Four out of 10 believe they work in a job which has a lower status than their fathers’ had when they were the same age. Respondents were asked to compare their own living standard with those of their parents. Although on average real material living standards have risen sharply, only half of middle-income respondents thought that their own living standard is higher than their parents’, 28 per cent think it is about the same and 17 per cent lower. Although they have high aspirations for themselves and their children, they also have high levels of frustration at their inability to fulfil them.

In the immediate postwar years British society resembled a ‘pyramid’ with a small and privileged group at the top, a larger but still small and comfortable middle and a large majority at the bottom. By the end of the 1970s, with the long-term decline of the manual working class and the spreading of affluence, Britain had moved closer to a ‘diamond’ shape with a small group of the rich and the poor and a much fatter middle. Today, it looks much more like an hourglass in shape, one with a small bulge at the top and a much larger one at the bottom.

The economic plight of ‘squeezed middle’ voters has, in part, made them politically footloose: helping first Margaret Thatcher, then Tony Blair and, most recently, David Cameron to power. Ed Miliband is just the latest of the party leaders to acknowledge the voting power of this vital group.

Photo: Victoria Peckham