http://www.usatoday.com/story/money/...-cars/2598657/
The linked USA Today article from 2013 lists the most frequently stolen luxury cars in the US. The BMW 3 series and BMW 5 series were on the list. As 02420X3 noted, model years are generally not compiled in such reports and some years may be more prone to theft.
While engine immobilizers and other security features introduced in recent models make thefts more difficult, some connected systems may present back doors for tech savvy thieves. This appears to be more of a problem in large metropolitan areas.
An expensive luxury car may be an attractive target for car theft and is much easier to steal if one can access keys. I had a friend that relocated near Houston and shipped her BMW 6 series with a transportation company. The company delivered the car but could not find her spare key. Rather than replace the missing key, she had a BMW dealer re-program her car for a new key but did not change the mechanical lock on the door. A few days later she found her car had been unlocked without triggering the alarm during the night. Burglars have been known to break into houses to acquire keys to luxury cars.
http://www.telegraph.co.uk/finance/n...efer-keys.html
One bit of good news for owners of cars with manual transmissions, these cars are less likely to be stolen in the US.
http://jalopnik.com/5937504/the-ten-...etting-stolen/