A growing number of insurers have come up with methods of tracking driving behavior and then using it to set a customer’s rates. Progressive claims that 70% of its Snapshot customers have seen a drop in their rates compared to what it was charging before – a discount of about $150 a year, on average. The industry giant says it will expand its auto insurance tracking program – even letting non-customers check it out – following studies that show the technology behind its “Snapshot” usage-based insurance is more than twice as accurate at discerning good drivers from bad.