DENVER -- Car owners buy glass-etching paste to burn their VIN permanently onto every window.

Rural sheriffs plant GPS tracking devices on farm tractors or four-wheelers left out as bait for machinery thieves.

Metro Denver cops drive cars with computerized license-plate readers that can sweep an entire grocery-store parking lot for stolen vehicles in a matter of seconds.

And it's all working. Automakers and police have waged a successful war on car theft in recent years, battering the stolen-vehicle rate by 20 percent to 30 percent annually.

A quick survey of the numbers offers some astonishing good news in a key crime category:

--Colorado vehicle theft dropped 22 percent in 2008, keeping 3,613 more cars with their rightful owners and saving an estimated $24.4 million in replacement value.

--Denver's rate dropped 30 percent in 2008, from 5,104 cars stolen the year before down to 3,591.

--Pueblo's rate dropped 67 percent.

--Nationally, the vehicle-theft rate was cut by more than half from 1991 to 2008, from 659 cars stolen per 100,000 population to 315 thefts. That rate drop effectively puts a security shield around more than 700,000 American vehicles a year.

Industry and law-enforcement experts attribute the gains to manufacturing innovations such as computer-coded car keys, as well as police cooperation across city lines in task forces dedicated to vehicle theft.

"It's a partnership between the engineering by automakers and the police efforts," said Colorado State Patrol Capt. David Santos, who works with the multijurisdictional Colorado Auto Theft Prevention Authority.

"There are still some ways to get around it, but we're working very diligently with industry and insurance companies on reducing the number of thefts. We're hoping that downward trend will continue," Santos said.

An added bonus of the auto-theft crackdown is breaking the link between the stolen vehicle and other crimes, Santos said.

Thieves often steal a car as part of committing another crime, whether carrying out a drug deal, a burglary or an assault. The stolen car can be crucial to the criminal's plans.

Insurance companies say the cut in thefts should eventually trim auto-insurance rates for consumers, though they can't yet quantify it.

Protection against theft loss usually makes up about 25 percent of the calculation for comprehensive coverage, said Carole Walker of the Rocky Mountain Insurance Information Association.

"If we can see (theft) come down over a few years, that does ultimately affect what you pay," Walker said. "It can have a big impact."

Auto-theft task forces allow local police investigators to cross lines in pursuit of stolen-vehicle rings and other leads.

Police departments can pool their resources to commit full-time detectives for auto theft, piecing together a wide range of information and creating more solid prosecutions against repeat offenders responsible for a big share of the cases.

The task forces are also benefiting from a law collecting $1 per vehicle from auto-insurance buyers. The fund now offers $3.5 million a year in grants to improve theft prevention.

The grants are paying for "license-plate reader" technology in area police departments.

The cameras use the same capture technology as tollbooth readers or photo-radar vans but can read plates during a cruiser's run through a parking lot or a packed street.

A computer instantly compares the license plates with those in a database of stolen vehicles or outstanding warrants, "pinging" the patroller on each match.

"The license-plate readers can read thousands of plates in the time it would take a person to run 20," said Jerry Cole, Western-states law-enforcement director for the anti-theft device LoJack, which works with police to track cars.

The combination of anti-theft devices, trackers, task forces and plate readers turns criminals paranoid, and that can make them informants, Cole said.

Washington County in northeast Colorado hopes to use the insurance-funded grants to update software that helped it crack down on a unique form of rural-vehicle theft.

Expensive farm equipment was disappearing from local dealerships, said Sheriff Larry Kuntz. An investigator got a warrant to place a GPS transmitter on a vehicle suspected of being involved in the thefts.

"When you see that tracked vehicle in the area of a lot of stolen vehicles, it helps you build a foundation for a case," Kuntz said.