Second, some have noted that, in many of the studies, there may be issues with selection bias since the introduction of CCTV was potentially endogenous to previous crime trends. In particular, the estimated effects may be biased if CCTV is introduced in response to crime trends. Has been argued that problems of selection bias and endogeneity can be addressed by stronger research designs such as randomized controlled trials and natural experiments. The Liberal Democrats were the only major party who…