Is it good or bad news when the number of poor kids in the UK wanting to go to university increases by nearly 20% in eight years? You might think that was a no-brainer: these figures, released yesterday by the British Market Research Bureau, are obviously positive.

But look at them another way and it looks less cheering: the gap between the educational aspirations of the richest and poorest children has not got any smaller since 2000. In Great Britain, while 78% of seven- to 16-year-olds in social class A want to go to university, only 55% in social class E do. In 2000, the figures were 67% and 46% respectively.

This kind of conundrum crops up again and again. It's a version of the so-called "poverty paradox". Poverty is generally defined relatively, so, for example, children in households earning less than 60% of the national median income are deemed to be poor. But, by this calculation, it is possible that as society gets richer, kids get better off in absolute terms, yet more of them are officially living in poverty. This is exactly what happened in Ireland as a result of its incredible growth in the 1980s and 1990s.

Of course, it is not always the case that you have to trade off absolute and relative wealth or opportunity. Sometimes we can all get better off without the gap between rich and poor growing too. Scandinavia managed to pull off this trick in the second part of the last century and, although doubters have been predicting the region's downfall for years, it's still pretty much working.

You might think that the paradox simply shows how silly it is to worry too much about equality. What matters is that people's life chances improve, and as long as they do, if those of others improve even more, what's the problem? Isn't it just the politics of envy to think that what others earn matters as much as what I do myself?

For many on the left, however, equality matters in itself. Even if people were generally richer in an unequal society, it would be better to have less wealth and less division into haves and have-nots.

It needn't be blind ideology that leads you to this conclusion. Some social science research has suggested that egalitarian societies are happier than inegalitarian ones, and that average life expectancy is related to equality as well as to wealth. Psychology has also shown that personal happiness depends on how you compares yourself to others, not just on how you are in yourself.

So the figures on educational aspiration really can be seen in two very different ways, depending on whether you focus on equality of aspiration or the total amount of it. Which way you choose is especially significant in Scotland, where the absence of student tuition fees is a source of pride, and seen as evidence of a fairer, more egalitarian outlook than in England.

But this equality may come at a price. The same survey that showed the aspiration gap had not been closed also showed that Scotland has seen the smallest increase in the proportion of children wanting to go to university in the whole country. Only 3% more Scottish children want to go to university (for free) than did in 2000, compared to an increase of 9% in Greater Britain (at a price) as a whole.

Scotland is still near the top of the league table for educational ambition, but it is no longer in first place. Could this be an example of how the egalitarian ethos is a factor in slowing the growth in life opportunities for all?

Any answer I give would be no more than a guess, but what is interesting is that, even if that were the case, it would not show Scotland's policy was wrong. It would still be open to argue that equality matters more than absolute life chances.

But how many advocates of a more equal society are prepared to say that slowing down the rate at which most of us get richer would be a price worth paying for it?

If you're prepared to bite that bullet, it may not be for entirely altruistic reasons. Psychology experiments have shown that people would rather have a smaller pay increase than a larger one, if that stops the gap between them and people earning more getting bigger.

Equality sounds like the noblest of objectives, but some of our reasons for wanting it are found in the darker side of human nature.

  • Julian Baggini is editor of The Philosophers' Magazine.