The UK population has risen by about ten million over the past 25 years — an increase of about 400,000 a year. Just over half of this is due to net inward migration and just under half is from the balance between births and deaths of the resident population. Population growth will continue.

Whether a continuing rise at this rate is a good thing is a hard question to answer. It raises some deep issues: how do we value the happiness of the unborn? How do we value the happiness that having a lot of children might bring? What about the costs from more congestion and the extra production of pollutants that more people is likely to bring?

When faced with a very difficult question,