For decades, scientists and economists have been making wagers about the outcome of human population growth. Now, more than ever, their speculations need to be taken seriously

In 2011, when the global population hit 7 billion, economist David Lam and demographer Stan Becker made a bet. Lam predicted food would get cheaper over the next decade, despite continuing population growth. Becker predicted that food prices would go up, because of the damage humans were doing to the planet, which meant that population growth would outstrip food supply. Becker won and, following his wishes, Lam has just written out a cheque for $194 to the Vermont-based nonprofit Population Media Center, which promotes population stabilisation internationally.

$194, about £140, equates to the amount by which a basket containing five food types – oils and fats, cereals, dairy, meat and sugar – and worth on average $1,000 in the decade to 2010, increased in price over the following decade, according to the UN Food and Agriculture Organization’s Food Price Index (FFPI) and allowing for inflation.