By Edward Hadas The opinions expressed are his own.

A child is born. For almost every parent, everywhere and always, the entry of a new person into the world is a welcome wonder. But economists generally have a different outlook on births. They prefer hard numbers to hope. And this week they have a big demographic number to discuss: the world’s population has just reached 7 billion.

When economists talk about demographics, Thomas Malthus usually comes up. The early 19th century British thinker decided (without providing any reasons) that people would always have more children than the physical world could possibly support. Population growth would always be restrained by death from want. At the time he wrote, the world’s population was about 1 billion. By the 1960s, the population had increased to about 3 billion people, and Malthus’s gloom was often cited. Some ecologists then claimed that the combination of industrial production and overpopulation would inevitably lead to environmental catastrophes – and many deaths from want.

And yet up to now, Malthus has been wrong, in two basic ways. First, human resourcefulness has proved much greater than he imagined. The economic story of the last two centuries has been one of increase – of people and production. The most recent years have been particularly impressive. The 135 million births this year will be almost 30 percent more than 50 years ago, according to UN data. Those lives will be longer; this year’s children can look forward to an average 68 years of life, 18 more than newborns a half-century ago. And the current crop will receive much more of the goods of industrial prosperity, from clean water and adequate food to free education and mobile phones.

Second, Malthus was wrong to assume that women would always bear just about as many children as physically possible. In the last 40 years, the total fertility rate, the number of children the average woman could be expected to bear, has declined from five to 2.5. The fertility reversal has reduced the annual rate of global population increase from 2 to 1.3 per cent since 1980. The UN expects that to fall to 0.1 per cent by 2085. An absolute population decline is quite possible. It is happening already in Japan and Russia.

Still, it cannot be proven that Malthus was wrong, that the world will never run out of stuff or that humanity’s resourcefulness will always rise to environmental, economic and social challenges. And yet – even though there is no way to persuade fervent Malthusians – after two centuries of steady progress the dire predictions look unduly pessimistic. The demographic slowdown reduces the danger of exhausting the earth’s physical resources. And while grim environmental forecasts are still easy to find, demographers these days talk more about the stresses that come with ageing and declining populations.