Are home security cameras a deterrent?

One purpose of security cameras and alarm systems is that they will turn potential intruders off attempting a break-in at all. The mere fact that they are obviously installed is hoped to deter thieves from considering your home as a target. If that doesn't do the job then the system's sensors, motion detectors, siren, and surveillance cameras go to work.

A 2015 study by the Australian Institute of Criminology looked into the reason for the 57% decline in burglaries between 2001 and 2009. The study involved asking offenders for their take on the reduction in break-ins over this time. The results indicated that improved home security was the most popular perceived reason for decreased home intrusions across Australia.

This study suggests that a security camera system, as well as other security measures, will actually act as a deterrent for would-be thieves. 

Ref - https://aic.gov.au/publications/tandi/tandi495