[E4qC1qQ5]

Probably about 0%

When I had a car in the city, I had it set for silent alarm and flashing lights. The silent alarm paged me, and the flashing lights let the potential car thief or drunks know that they had triggered an alarm. I wouldn't have heard an audio alarm from my apartment anyway, and i saw no reason to piss off anybody trying to get some sleep

[chuviskkk]

There's a car right outside my apartment that has that problem. It's in the carport next to mine. One time it went off when I got in my car & slammed the door. There was one night this winter when it was bitter cold, it went off 7 times. Fortunately, I'm a night owl, so I was up, as opposed to being asleep and woken up time & time again. I can't believe the owner was so insensitive to keep resetting the damn thing.

More recently, when it went off multiple times, some mom left a big note to get it fixed, it keeps waking her & her child up. If not she was going to (I couldn't read it all from my window). Since then, I haven't heard it, so hopefully the owner got it fixed.

[excivaamome]

To answer the question - very low.

http://www.transalt.org/info/caralar...effective.html

Once a matter of debate, the evidence is now clear: car alarms, for all their sound and fury, do nothing whatever to stop car theft or theft from within cars. "Car alarms are a terrible urban blight with obvious social costs - noise pollution, increased stress, wasted police manpower dealing with broken alarms - and it's not clear there are any benefits in return," says Lawrence Sherman, director of the Jerry Lee Center of Criminology at the University of Pennsylvania. "No study has demonstrated that they reduce auto theft."16

[joeyCanada]

Ahh.

http://www.silentmajorityny.org/links/hldi-article.pdf

The HLDI which is insurance company funded (and thus can be expected to be reasonably unbiased, as the insurers have an incentive to figure out the right answer to this and thus support or not support alarm-related premium adjustments) found that there was no significant effect on theft of car alarms.

What I have seen in looking briefly is that the major things are LoJack (which is not an effective deterrent, but significantly reduces theft in the whole area due to criminals being less likely to steal cars in an area with a lot of LoJacks, and presumably due to criminals being caught more often), steering wheel immobilizers, and such. Clubs don't deter crime, but they do deter YOUR car from being stolen, which is the selfish but reasonable point of view