Having worked in Insurance for my working life I can confirm the figure is very high. Working for one of the largest companies we had two full time ex senior police officers in Scotland working full time with a high salary. They were able to easily cover their costs in sorting these problems, but what got through we will never know.
The ones detected tended to fit a fixed pattern that would show up against a set of given criteria.
my daughter also worked on fraud claims at one time for another company.
One of the most blatant reported was a hotel that burned down with no guests despite the fact that it was allegedly fully booked. At the other end paint, supposed to have been spilled on a TV and video which when examined had brush marks showing deliberate painting of them.
We saw altered invoices and receipts, and one of the most blatant was a haulier who tried to claim for writing of an artic tractor unit twice, after keeping the salvage following the first incident.
What the people did not anticipate was that even on minor claims we reported them to the police and several ended up not only unable to get insurance but also with criminal records.
i could probably write a book on this but people might find it hard to believe some.