This article is based upon data from the German Insurance Association. Some car immobilizers can be defeated in less than an hour due to weak encryption. It would take a somewhat sophisticated thief to do this.
http://www.newscientist.com/article/mg20827894.500-criminals-find-the-key-to-car-immobilisers.html
http://www.newscientist.com/article/mg20827894.500-criminals-find-the-key-to-car-immobilisers.html