Does installing an alarm system in your home have an effect on the number or results of burglaries?

I am about to buy a house with an alarm system installed, with a siren/flash light on the front wall. I hate it when I have to enter a house like that, because I fear forgetting or mistyping the code, or arming the system when I want to disarm it, or just being too late because my hands were full.

If I would leave the system permanently disarmed, should I expect an increase in the number or effect of burglaries? I think the number will probably stay the same: thieves can't know the system is not armed (or even fake). Once they get in they might have more time to steal stuff, but I think the psychological effect of a burglary is the fact that they entered your house, not how long they stayed there.

I have read that car alarms don't make much of a difference, but what about house alarms? One indicator is the fact that insurance premiums here in Belgium don't seem to depend on an alarm being installed.

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    Was a very interesting paper presented at last year's Scottish Financial Crime Conference (will try and find an online version) which did indicate alarm systems definitely helped (attackers would often go on to the next building), automatic lights actually helped burglars (the kind that light up your back garden when a cat passes by) but that the best protection was alarms connected to either police or local security, along with notices to that effect. – Rory Alsop Mar 10 '12 at 12:58
  • If you are concerned for the actual trespassing, regardless of whether anything gets stolen, an active or disabled alarm system provides the exact same level of deterrent. Related to the alarm itself, the biggest deterrent is the signage signifying that your home is equipped with an alarm. The second deterrent is the noise the alarm makes should the trespasser ignore or not notice the signage. Like @RoryAlsop said, motion activated lights and night-active flood lights also provide excellent deterrence. – jdstankosky Nov 1 '12 at 15:13

Yes, the use of burglar alarm as a target hardening crime prevention tactic and micro level approach for crime prevention is supported by the study ‘The Impact of Home Burglar Alarm Systems on Residential burglaries'. In a report submitted to alarm Industry Research and educational foundation by Lee, PHD the question “do home burglar alarms have the deterrent effect on residential burglary?” was answered by analyzing the phenomenon between the gradual decrease of residential burglaries and the increase of residential burglar alarms in Newark, N.J.

Prior studies suffer from some methodological shortcomings since in most of those earlier studies, the methods of evaluation met minimal standards, had short followup, and reliable control groups were generally absent Clarke, 1995; Weisburd, 1997. This study resolved several issues present in the earlier studies. However several limits inevitably subsisting in this study are also discussed in the report.

The conclusions of the study were,

The continual decrease of the number of residential burglaries was closely and statistically associated with the consistent increase of burglar alarm installations in Newark, N.J. Chi-square and changed proportion statistics supported the crossing relation was statistically significant and persistent over the years, which indicated that burglar alarms impacted on the decrease of residential burglary incidents.

Spatial analyses suggested that burglar alarms had some positive impact on residential burglaries on the city level by showing that hotspots of burglar alarms did not overlap those of residential burglaries. Finally, the applied WDQ analysis revealed that no indication of spatial displacement of residential burglary due to the increase of burglar alarm installations was observed and that there was a positive and substantial impact of burglar alarms on the progressive decrease of residential burglaries over the years.

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