Fit good locks on doors and windows, put a motion-sensor light outside the door, and really lock up when you go out: these are what prevent burglary, and an alarm alone shows no benefit

Cost

Replacing the door lock with one that must be locked with a key, adding window locks and putting a motion-sensor light outside the door generally costs a few dozen to a few hundred CNY. Replacing the whole security door costs over 1,000 CNY. The hard part is truly locking doors and windows every time you leave, and remembering to do so in summer when windows are open.

What you get

The Crime Survey for England and Wales asked 37,416 households in 2008 to 2012 which security measures they had, and compared them with households that were burgled. Households with nothing installed made up only 4.9% of all households, but 36.6% of households where someone got in and stole. The authors calculated a "protection multiple": how many times lower the burglary chance is than that of households with nothing. Door locks plus window locks give 12.54, so the burglary chance falls to about one-twelfth. Here a door lock means a double lock or a "deadlock" (one whose bolt can be retracted only with a key). Door locks and window locks plus a motion-sensor or timer light outside the door give 34.41. Adding a timer light inside the house gives 49. For a single measure, the light outside the door gives about 3 and the door lock about 2.8. Window locks alone show no difference. Having all five measures is no better than the right three. Installing only an alarm and nothing else, the burglary chance is actually higher than with nothing. Households with a fake alarm box also had a higher chance of attempted break-ins that did not succeed. Locks count only if they are really locked: from 1993 to 2006/07, burglary by forcing locks, smashing windows or taking apart door panels fell from 31 to 7 per 1,000 households, a fall of 77%. The kind where doors and windows were unlocked and someone simply walked in stayed at 7 per 1,000 households and did not fall (England and Wales)

Notes

Dispute: there is counter-evidence on the alarm half. The same authors, using data from 1992 to 1996, found that back then adding an alarm did lower the burglary chance. The authors also say this odd result should be treated with caution; one possibility is that households that had been burgled were the ones that installed alarms. All the figures are from Britain and only compare households that had the measures with those that did not, with no controlled groups, so this is graded B. These figures cover only burglary, and there is no data saying door locks can stop robbery in the home. If you do find someone in the house, back away and call the police first; see §8.10 (call the police and don't hit back when a conflict starts). If you are cornered, see §8.11 (you may fight back against an attack you can't avoid). If you rent, agree with the landlord first before changing locks or adding window locks. The Civil Code (民法典) provides that if a tenant adds or modifies something without the landlord's consent, the landlord can require restoration to the original condition or compensation. When buying a security door you can check one thing: security doors have a mandatory national standard, GB 17565-2022, in effect since January 1, 2024. The beneficiary is mainly you and your family.

Evidence grade

B : Supported by research but without a precise number, or based on small or single studies.

Sources

1. Tseloni A, Thompson R, Grove L, Tilley N, Farrell G (2017). The effectiveness of burglary security devices. Security Journal 30(2):646–664. https://doi.org/10.1057/sj.2014.30
2. Tilley N, Thompson R, Farrell G, Grove L, Tseloni A (2015). Do burglar alarms increase burglary risk? A counter-intuitive finding and possible explanations. Crime Prevention and Community Safety 17(1):1–19. https://doi.org/10.1057/cpcs.2014.17
3. Tseloni A, Farrell G, Thompson R, Evans E, Tilley N (2017). Domestic burglary drop and the security hypothesis. Crime Science 6:3. https://doi.org/10.1186/s40163-017-0064-2
4. 国家市场监督管理总局、国家标准化管理委员会 (2022). GB 17565-2022 防盗安全门通用技术条件. https://openstd.samr.gov.cn/bzgk/gb/newGbInfo?hcno=A75C1C66CB989D0A40BFA7A262C93290
5. 全国人大 (2020). 民法典（第七百一十五条）. https://www.spp.gov.cn/spp/fl/202006/t20200602_463888.shtml

Translated from the Chinese original. Original book, section 8, tip 46. This section describes legal rules, mostly mainland China’s. It is general information, not legal advice; for your own case, talk to a lawyer. Content may be out of date and rules differ by place. When you actually deal with an agency, a doctor or a court, follow what local officials, doctors and lawyers tell you. Disclaimer