What statistics are available that indicate how often or what percent
of the time people with security systems in their homes actually use them?

< Research from the British Security Industry Association and the DTI
found that of those with an alarm, 39% set it all the time, 15% if
they are going out overnight, 10% never set it and 28% set it when
they go to bed.
http://www.bsia.co.uk/bsia_news.taf?_function=detail&_record_uid1=32865

According to a survey by Norwich Union, one third of those with alarms
do not always activate them when they leave the house.
http://www.nu-riskservices.co.uk/news/specials/cms/10827396281141722023482_1.htm

An NOP survey of burglars found that 1 in 20 households don?t turn on
their burglar alarms.
http://66.102.9.104/search?q=cache:iA_yvGtG73YJ:www.tvnewsrelease.com/upload/docs/doc_53.doc+%22have+burglar+alarms%22+%22don%27t+use%22&hl=en

A survey from Royal Bank of Scotland Insurance Services found that
just 78% of people would set their burglar alarms whilst on vacation.
(Source: Homes at Risk While Holiday Makers Away. 20 October 2003. The
Royal Bank of Scotland Group.)
http://www.rbs.co.uk/Group_Information/Newsroom/Press_Releases/2003/October/20_homes_risk.htm


An Australian survey found that 47% of men and 31 percent of women
forget to switch on their alarm when they leave their house. (Source:
Care and home security index 2004.)
http://216.239.59.104/search?q=cache:arCZMYLMNKYJ:www.aami.com.au/about_aami_insurance/aami_news_centre/pdf/special_reports/specialreports_securityindex_2004.pdf+%22home+security%22+%22forget+to+switch+on%22&hl=en

In houses burgled with alarms fitted, over 85% of burglar alarms were
not switched on or being used properly. (Source: Burglaries cost
households E58m. Irish Examiner. November 11, 2004.)
http://archives.tcm.ie/irishexaminer/2004/11/11/story87096621.asp


A national survey by NFO WorldGroup  of almost 3,000 people found that
of those that have a home security system, 55% are less than certain
of how to operate it. (Source: YENRA)
http://www.yenra.com/home-security/


According to Honeywell 30% of people turn on security system before
going on vacation. (Source: Americans On The Go. Honeywell.)
http://content.honeywell.com/yourhome/pr_travel.htm



In New Zealand, 2/3 of people set their alarm at night. (Source: Kiwis
Tighten Home Security. 20/12/2004. Xtramsn.)
http://xtramsn.co.nz/technology/0,,7005-3955872,00.html>


<Search strategy:>

<"forget to switch on the alarm">
<://www.google.com/search?hl=en&lr=&q=%22forget+to+switch+on+the+alarm%22>

<respondents "security systems" homeowners>
<://www.google.com/search?hl=en&lr=&q=respondents+%22security+systems%22+homeowners>

<"home security systems" survey remember>
<://www.google.com/search?q=%22home+security+systems%22+survey+remember&hl=en&lr=&start=10&sa=N>

survey "set their alarms"
://www.google.com/search?q=survey+%22set+their+alarms%22&hl=en&lr=&start=20&sa=N

<Hope this helps.>

Very good perspective and references!