How effective are car alarms for preventing cars being stolen?
I would guess that cars of similar type with car alarms are stolen no more than 5 percent less than cars without alarms. I suppose each of us has to weigh whether the reduced risk is worth the hassle to ourselves and neighbors when, as too often happens, the thing goes off inadvertently. A careful answer should address the fact that expensive cars are both worth more to steal and worth putting up with more hassle.
The car alarm is completely useless nowaday because everybody is so d@mn tired of hearing the alarm that we simply ignore.
I would recommend the “Low-Jack” from the police station instead.