Do car alarms provide a significant reduction in automobile theft?

Do car alarms provide a significant reduction in automobile theft?

• http://www.imdb.com/title/tt0425308/ That movie got me thinking, because it makes a number of claims about car alarms that jive with my personal feelings about them. They're noisy, obnoxious, tend to go off at night, and are almost universally ignored by passersby, people in nearby houses, and the car owners themselves. Despite these flaws, having one is almost default for new automobiles, and you even get a discount on insurance if you have one. So the question is: Do car alarms actually reduce the incidence of theft of or from automobiles in which they are installed? If so, by how much? Whether or not the reduction (if any) is worth the hassle and noise will, of course, be a matter of opinion. Edit: I'm not, of course, referring to car security systems in general. I'm only questioning the usefulness of the loud noise making aspect of them.

• Answer:

  Audible car alarms do not have a significant effect on car theft. The insurance data are unequivocal. In 1997, the non-profit Highway Loss Data Institute (HLDI) surveyed insurance-claims data from 73 million vehicles, to see which devices could prevent theft. Looking at cars from many different model years, across the country, the study concludes that cars with alarms "show no overall reduction in theft losses" compared to cars without alarms. http://www.transalt.org/files/newsroom/reports/caralarms/08ineffective.html "Alarmingly Useless, The Case for Banning Car Alarms, in New York City", by Aaron Friedman, Aaron Naparstek & Mateo Taussig-Rubbo There are a variety of antitheft and tracking systems on the market with costs ranging from basic audible alarms costing $50 to sophisticated tracking systems with $30 monthly fees. Unfortunately, the effectiveness of many of these devices is questionable. The sensitivity of audible alarms to touch or movement, for example, provokes a “boy who cried wolf” reaction. When a car alarm goes off, people tend not to react because the alarms activate so frequently for reasons other than actual theft. HLDI studies show no overall reduction in theft losses for vehicles with such alarms. http://www.silentmajorityny.org/links/hldi-article.pdf Highway Loss Data Institute, "Insurance industry analyses and the prevention of motor vehicle theft," Business and Crime Prevention (Marcus Felson and Ronald V. Clarke, eds.), pp. 283-93, Monsey, NY: Willow Tree Press, Inc.: 1997