iPhone thefts have been dropping dramatically in at least three major cities since Apple introduced its Activation Lock feature in 2013, Reuters reports. Specifically, the number of stolen iPhones in San Francisco has reportedly dropped by 40 percent, while the number of iPhone thefts in New York has dropped by 25 percent, and smartphone theft in general has dropped by half in London. The drop is believed to be a direct result of the anti-theft features that Apple added to iOS 7 in September 2013, which effectively “locked” an iOS device to its owner, preventing a stolen device from being used without entering the original user’s Apple ID and password. Supplementing the “Find My iPhone” feature introduced by Apple some time ago, the new Activation Lock feature essentially turns a stolen iPhone into a useless brick, reducing the motivation for theft. With smartphone theft now accounting for half of all crimes in cities like San Francisco, several U.S. states are considering laws mandating the use of similar “kill switches” in smartphones — California passed a smartphone “kill switch” law last year that has yet to go into effect. While Samsung and Google have added a similar feature, only Apple currently has it setup to be enabled by default.