In the past, if a burglar was caught having broken into ten houses, it was recorded as a single incident — one criminal = one crime.
The government at the time decide that this was misleading the tax-paying public. There were ten victims so it should be recorded as ten crimes.
But what happens if you have 200 people bursting through the windows of a JD Sports store to help themselves to new trainers? There is only one ‘victim’ so it counts as one crime, even if all 200 are prosecuted separately.
More to the point, those 200 were otherwise occupied when they might have been unlawfully occupied in smashing up bus shelters or shop-lifting in Lidl, so all those individual crimes that might have been committed elsewhere didn’t happen.
There is a more erudite explanation over at The Independent, but it is a reminder that statistics are like a bikini. What they reveal is suggestive, but what they conceal is vital.