According to the officials, in San Francisco, overall robberies and thefts dropped 22 per cent from 2013 to 2014, but those involving smartphones were down 27 per cent. Thefts and robberies of iPhones fell 40 per cent.
    
In New York, smartphone theft dropped 16 per cent overall with iPhone figures down 25 per cent.
    
London saw smartphone thefts drop 40 per cent in a year, 'pcworld.com' reported.
    
"The huge drops in smartphone theft that have occurred since the kill switch has been on the market are evidence that our strategy is making people safer in our cities, and across the world," said New York State Attorney General Eric Schneiderman.
    
The kill switch is a software lock that can be remotely activated when a phone is lost or stolen.
    
It can wipe personal data from a phone and "brick it" so it can't be reused or reprogrammed.
    
Apple added a kill switch, called Activation Lock, to its iPhone in September 2013. Samsung followed in April 2014 with its Galaxy S5 and Google made it a standard feature of Android with the release of Lollipop.