According to the latest Federal Bureau of Investigation (FBI) report:
There were an estimated 721,053 thefts of motor vehicles nationwide in 2012
In the U.S. one vehicle is stolen every 43.7 seconds
More than $4.3 billion was lost nationwide to motor vehicle thefts in 2012
22 states had year-over-year increases in vehicle theft in 2012 vs. only 19 states in 2011
The national recovery rate of stolen vehicles is 54%. Nearly half of the vehicles stolen in 2012 were never returned to their owners – amounting to 331,684 vehicles.
In fact, 73.9% of all motor vehicles reported stolen in 2012 were automobiles and the average dollar loss per stolen vehicle was $6,019.
Source: FBI Uniform Crime Report (2012)
Most car thieves are part of extremely organized crime rings and know how to steal any car they want. Locked doors won't stop them and security systems don't scare them off.