In 1960, there were just over three billion people alive in the world; now there are close to seven billion. So the global population of humans has more than doubled in 50 years. But at the same time people around the world have demanded more and more meat. (Consumption of animal products tracks closely with income, and, in the long term, per capita income has risen hugely.) So what has that meant for global livestock populations? Massive, massive growth.
In 1961, there were 3.9 billion chickens on earth, just over one per person. Now there are 19 billion, according to UN data analyzed by the Economist. That's three for every person alive. The next most populous livestock is cattle; there are 1.4 billion of them.
Wild animals, meanwhile, have not fared as well. Since 1960, the global population of wild animals have tumbled by a quarter.
[Via @caraparks, HuffPost World Editor.]