Number cruncher

Levels of migration into Britain are a controversial issue. In the three decades prior to 1998, net migration was, on average, close to zero. Since 1998, average net migration has exceeded 150,000 per annum.

Those in favour of migration argue that migrants do jobs that natives don't want, pay taxes, make the labour market more flexible and are good for growth. Those against argue that they limit job opportunities for natives, hold down wages, add to overcrowding and consume public services.

The economic consequences of permanent migration depend on the extent to which migrants are like natives. If they have the same age and skill sets as natives, then in the longer term the economy retains the same structure, but with a larger population.



If migrants are more skilled, harder working and more likely to be of working age than natives, there are short-term benefits, as they pay more taxes and consume fewer public services. The opposite applies if they are less skilled and so on. Over the longer term these effects moderate as migrants increasingly resemble natives the longer they remain. In the long run, the economic impact of net migration tends to be small but positive.

Over the longer term, we must also consider whether a larger population is compatible with our fixed land area. Take housing. Urban areas in England, the most crowded part of Britain, are around 12 per cent of total land. At the rate of housebuilding over the last decade, the loss of rural land to new housing proceeds at a rate of about 1 per cent of English land every 40 years.

But, of course, a growing population means not only more housing but more roads, airports, energy consumption and waste disposal. On the one hand, expressed preferences are usually against new houses, runways and power stations (at least if they are near those whose preferences are being expressed). On the other hand, the extra space required for these things is not very great. So the fundamental migration question is: does the negative weight of these preferences outweigh the small long-term economic benefits? This is where the argument should be focused.