There have been a myriad of reasons suggested for the steady fall of petty and violent crime across America since the early 1990s. The Freakonomics guys controversially suggested it may have occurred because legalized abortion had diminished the population of unwanted children. But the trend America has experienced has spread across the globe in the decades that followed, and not all of those countries have similar abortion laws. Is is because of criminology, technology or shifting demography? All of these things combined? From “Where Have All the Burglars Gone?” in the Economist:

“Both police records (which underestimate some types of crime) and surveys of victims (which should not, but are not as regularly available a source of data) show crime against the person and against property falling over the past ten years in most rich countries. In America the fall began around 1991; in Britain it began around 1995, though the murder rate followed only in the mid-2000s. In France, property crime rose until 2001—but it has fallen by a third since. Some crimes are all but disappearing. In 1997, some 400,000 cars were reported stolen in England and Wales: in 2012, just 86,000.

Cities have seen the greatest progress. The number of violent crimes has fallen by 32% since 1990 across America as a whole; in the biggest cities, it has fallen by 64%. In New York, the area around Times Square on 42nd Street, where pornographers once mingled with muggers, is now a family oriented tourist trap. On London’s housing estates, children play in concrete corridors once used by heroin addicts to shoot up. In Tallinn you can walk home from the theatre unmolested as late as you like.

What is behind this spectacular and widespread improvement? Demographic trends are an obvious factor. The baby-boom in the decades after the second world war created a bubble in the 16- to 24-year-old population a couple of decades later, and most crimes are committed by men of that age. That bubble is now long deflated. In most Western countries, the population is ageing, often quite fast.

But demographics are not everything.”