It's fun to steal cars in Grand Theft Auto. In the real world, thefts have dropped by half since 1991.

Grand Theft Auto may be one of the most popular video games, but it seems like the real crooks are going into another line of business.  New data show that car thefts continue to tumble – in part due to improved security systems on new vehicles – and have hit a 20-year low.

The Federal Bureau of Investigation estimates that just 956,846 motor vehicles were stolen in the U.S. last year.  While that may sound like a lot, that figure compares with the record 1.66 million vehicles stolen in 1991.  And that doesn’t fully reveal the dramatic decline.  There are more people in the U.S. and significantly more cars, trucks and crossovers on the road now, so the 2008 data equal 315 cars for every 100,000 people, down from 659 per 100,000 in 1991.

Experts debate the reasons behind the reduction in car theft.  Some point to new technology, such as ignition immobilizers, which prevent an engine from starting unless you use the correct, digitally-encoded key.  There are several different systems now available to motorists and authorities which help track stolen vehicles, including a new service recently launched by the General Motors subsidiary OnStar.

Meanwhile, there have been a number of federal, state and local programs created to both prevent car thefts or at least catch the perpetrators, including HEAT, short for Help Eliminate Auto Thefts.  And in many jurisdictions, the courts have become tougher on thieves who, in decades past, may have been able to avoid jail time.

Another program, in Arizona, yielded a 25% decline in car thefts, just between 2007 and 2008, by focusing on organized rings that would often hire petty criminals to bring them vehicles that would then be stripped of their engines and other parts that could be quickly resold.  It was a common site to see the bare frames of stolen vehicles dumped on back streets in cities like Phoenix, Newark and Detroit.  Authorities tell TheDetroitBureau.com that a well-trained “chop-shop” can hack apart a stolen vehicle in a matter of minutes.

Additionally, authorities have taken a closer look at parts shops and shady repair shops that may use those stolen pieces.  In some cases, manufacturers are now marking sheet metal and parts to make it easier to separate legitimate replacement components from those yanked off a stolen vehicle.

“It’s a much tougher job to be a car thief today,” Russ Rader, spokesman for Highway Loss Data Institute, a research group funded by auto insurers, told the Detroit Free Press.

As to the most stolen cars, HLDI’s most recent report points to the 2007 Cadillac Escalade ESV which, when you compare the number of those vehicles on the road, is the most likely to have someone unauthorized drive it away.  The theft rate is 15 per 1,000.  The second most common vehicle is the 2005 through 2007 Ford F-250 SuperCrew, with a theft rate of 13.1 per 1,000.

While auto theft rates have declined across the country, there are some hot spots given vehicle owners, police and insurers headaches.

“The bad news is that the theft rate continues to increase in areas like El Paso and Laredo where many of the cars, trucks and SUVs being stolen are being used to carry drugs, money and weapons into and out of Mexico. These vehicle thefts are helping finance the drug cartels that are waging war on the Mexican government,” Joe Wehrle, president and chief executive officer of the National Insurance Crime Bureau, told TheDetroitBureau.com.

The latest auto theft data covers through 2008.  The numbers for 2009 are not yet available.  But authorities across the country are providing anecdotal reports that suggest that even if vehicle thefts will hold low for the year, they’re seeing an increase in so-called “smash-and-grab” crimes, where robbers break a window and grab a purse, radio or navigation system, or even pull expensive wheels off parked vehicles.