The United Nations Population Division is the go-to source for demographic data covering everything from urbanisation rates to old age life expectancy.

But now Sanjeev Sanyal, a global strategist at Deutsche Bank, has questioned the UN’s latest global population forecasts – a stunning act of lèse-majesté.

In a paper released this week, he argued that total fertility rates (TFR) among women in fast-growing economies are already falling so fast that the UN predictions – relied on by demographers, sociologists and economists all over the world – simply cannot be credible.

 

The UN’s latest numbers suggest that world population, currently at around 7.2bn, will rise to 9.6bn by 2050 and then further to 10.9bn by 2100.

By contrast, Mr Sanyal forecasts that global population will peak in less than 50 years’ time. This week he set out his views in a briefing note in which he described himself as a “rogue demographer”.

“We forecast that world population will peak at around 8.7bn in 2055 and will then decline to 8bn by 2100,” he wrote. “Thus, world population could peak half a century sooner and, by 2100, stand 2.8bn below what the UN currently predicts.”

In making his forecast, Mr Sanyal pointed to two things: the first is that even by the UN’s own projections, urbanisation is happening in the developing world at a very rapid rate.

He noted that the UN projects that the percentage of global population living in cities will rise to 67 per cent by 2050 from 52 per cent today – a forecast he deems “reasonable”. And that does not square with the level of fertility implied by the UN’s population growth forecast.

“Urbanisation is the strongest contraceptive known to man,” he wrote. “Every known society has witnessed large declines in birth rates as it has urbanised, irrespective of cultural background.”

Secondly, total fertility rates have already fallen very rapidly in many fast-growing countries between 1985 and today, sometimes by half. For example, over the past 30 years alone, fertility in Brazil has fallen by roughly half.

Another example is that of Iran. And while countries such as Mexico and Indonesia have not seen declines as dramatic as that of Brazil, the overall trend remains the same.

“Given the above trends, we feel that the world’s overall fertility rate will fall to replacement rate by 2025,” Mr Sanyal wrote. “In other words, reproductively speaking, our species will no longer be expanding.”

If that happens it would indeed be, as Mr Sanyal concluded, “a major turning point in history”.