Install proper locks on doors and windows and an outdoor motion‑sensor light; always actually lock them: these steps help prevent burglary, but a single alarm alone won’t do much

Cost: Replacing a door lock with one that requires a key to re‑lock, adding window locks, and installing a motion‑sensor light outside generally costs from a few dozen to a few hundred yuan. A whole new security door can run into thousands of yuan. The real challenge is remembering to actually lock everything each time you leave — even in summer when windows stay open.

In plain terms: British data shows that homes with both door and window locks have only about one‑twelfth the burglary rate of homes with no such measures. Adding an outdoor motion‑sensor light further reduces that risk to roughly one‑thirtieth. Installing just an alarm, without any other measures, provides little to no protection. These steps guard against theft, not against a robbery when someone is already inside the house.

Benefit: A crime survey in England and Wales asked 37,416 households between 2008 and 2012 which security measures they had installed, then compared those figures with actual burglary rates. Households with nothing installed made up just 4.9 % of all respondents yet accounted for 36.6 % of burglary victims. The researchers calculated a “protection factor” — how many times lower the burglary risk becomes compared to homes with no measures at all. Door and window locks together give a protection factor of 12.54, cutting the risk to roughly one‑twelfth. Here “door locks” refers to double‑bolted locks or deadbolts that need a key to retract. Adding an outdoor motion‑sensor or timer‑controlled light raises that factor to 34.41; adding indoor timer lights pushes it to 49. A single motion‑sensor light offers only about a 3‑fold benefit, while a door lock alone gives roughly a 2.8‑fold improvement. Window locks alone show no measurable effect. Installing all five measures does not yield a noticeably greater benefit than using the three most effective ones. Conversely, homes that install only an alarm actually experience a higher burglary rate than those with no measures at all; even fake alarm boxes seem to increase the chance of an attempted break‑in. The key is actually locking everything: from 1993 to 2006/07, forced‑entry burglaries — where thieves pried locks, broke windows or kicked in doors — fell from 31 to 7 per 1,000 households, a 77 % drop. In contrast, burglaries where the door or window was left unlocked and the intruder simply walked in stayed at 7 per 1,000 households throughout the same period (England and Wales).

Evidence grade: B

Sources: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；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；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；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；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

Notes: There is some debate regarding alarms: the same authors previously found, using data from 1992‑1996, that alarms did lower burglary risk. They caution that this contradictory finding may reflect selection bias — perhaps only households that had already been burglarized later installed alarms. All figures pertain to the UK and compare households with and without certain measures; no randomized controlled trials were conducted, which is why the evidence grade is B. These statistics apply solely to burglary, not to home invasions or robberies. If a stranger does enter while you are inside, retreat to a safe area and call the police (see point 10). Should escape be impossible, you may use reasonable force to protect yourself (see point 11). Tenants should obtain landlord permission before changing locks or adding window locks; under civil law the landlord may demand restoration to the original state or compensation. When buying a security door, look for compliance with the mandatory national standard GB 17565‑2022, effective from 1 January 2024; the primary beneficiaries are you and your family.