There's been a widespread trend in developed/western nations of falling crime rates over the last 20-odd years, yet nobody's 100% sure why.
http://www.economist.com/news/briefi...t-and-economic
Quote:
Across the developed world, the crime wave that began in the 1950s is in broad retreat (see chart 1).
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.
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Of course, you could see this as proof that policing has worked wonders over the last 20 years, but when the level of crime is on a downward trend, you don't need to recruit an increasing number of coppers.