According to the latest Federal Bureau of Investigation (FBI) report:
There were an estimated 715,373 thefts of motor vehicles nationwide in 2011
In the U.S. one vehicle is stolen every 44 seconds
More than $4.3 billion was lost nationwide to motor vehicle thefts in 2011
19 states had year-over-year increases in vehicle theft in 2011 vs. only 12 states in 2010
The national recovery rate of stolen vehicles -- 52% -- is at 30-year low. With this drop, nearly half of the vehicles stolen in 2011 were never returned to their owners – amounting to 371,800 vehicles.
In fact, 73.9% of all motor vehicles reported stolen in 2011 were automobiles and the average dollar loss per stolen vehicle was $6,089.
Source: FBI Uniform Crime Report (2011)
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.