Worries about a population explosion have been replaced by fears of decline. The population of bugs in a Petri dish typically increases in an S-shaped curve. To start with, the line is flat because the colony is barely growing. Then the slope rises ever more steeply as bacteria proliferate until it reaches an inflection point. After that, the curve flattens out as the colony stops growing reports the Economist.

Overcrowding and a shortage of resources constrain bug populations. The reasons for the growth of the human population may be different, but the pattern may be surprisingly similar. For thousands of years, the number of people in the world inched up. Then there was a sudden spurt during the industrial revolution which produced, between 1900 and 2000, a near-quadrupling of the world’s population.

Numbers are still growing; but recently—it is impossible to know exactly when—an inflection point seems to have been reached. The rate of population increase began to slow. In more and more countries, women started having fewer children than the number required to keep populations stable. Four out of nine people already live in countries in which the fertility rate has dipped below the replacement rate. Last year the United Nations said it thought the world’s average fertility would fall below replacement by 2025. Demographers expect the global population to peak at around 10 billion (it is now 6.5 billion) by mid-century.

As population predictions have changed in the past few years, so have attitudes. The panic about resource constraints that prevailed during the 1970s and 1980s, when the population was rising through the steep part of the S-curve, has given way to a new concern: that the number of people in the world is likely to start falling.

Some regard this as a cause for celebration, on the ground that there are obviously too many people on the planet. But too many for what? There doesn’t seem to be much danger of a Malthusian catastrophe. Mankind appropriates about a quarter of what is known as the net primary production of the Earth (this is the plant tissue created by photosynthesis)—a lot, but hardly near the point of exhaustion. The price of raw materials reflects their scarcity and, despite recent rises, commodity prices have fallen sharply in real terms during the past century. By that measure, raw materials have become more abundant, not scarcer. Certainly, the impact that people have on the climate is a problem; but the solution lies in consuming less fossil fuel, not in manipulating population levels.

Read it here: http://economist.com/opinion/displayStory.cfm?Story_ID=9545933