Further to "The biggest deterrent to car thieves is to try and steal vehicles which have factory fitted immobilisers and alarms. As you will have noticed all vehicles less than 10 years old have these fitted and how many are stolen? Very few."
Very few?! Er, no. Lots and lots actually. Retro quite correctly mentions hook and cane but in most of the areas I currently fly, new cars are being stolen using keys taken from simple break ins. These lovely new vehicles (all fully immobiliser and alarm fitted) are then often used to transport away goods from the house in question. In my own current experience, when air support is overhead on these incidents, these vehicles and goods are always recovered (and suspects arrested). Without air support, they usually get away.