Thomas Malthus forever attached the word "dismal" to "economics". The argument of the 19th century sage that rising population would offset any tendency towards rising standards of living was as depressing as it has since proved incorrect. Malthus was not the first prophet to underestimate human ingenuity. He will not be the last.

Yet Malthus was right to believe that demography is always important. As this month's World Economic Outlook from the International Monetary Fund makes plain, demographic forces will drive the world economy in the decades ahead.* Three big things are now happening. First, fertility rates - the number of children produced by each woman - are falling rapidly almost everywhere. Second, life expectancy is also rising almost (though not quite) everywhere. Third, developing countries are well behind the advanced countries, with the poorest countries furthest behind of all.