This post first appeared on the Social Research Association blog. Understanding if some event is associated with a change in the frequency of crime is a common question, both in practice and in research. A crime analyst might need to understand the impact of a change in tactics, a local journalist might want to check the truth of the mayor’s claims that her policies are working, while an academic might seek to find patterns associated with trends in socio-economic changes.

Some serious crime investigations are surprisingly quick: half of murder prosecutions involve a suspect being charged in five days or fewer. But for many serious crimes, justice is often slow: half of fraud prosecutions don’t conclude until almost two years after the crime occurred.

larger image | annotated R code to produce this chart

Data source: Ministry of Justice, 2019

Once police have enough evidence to prosecute an offender, they or prosecutors must decide whether to send the case to court or deal with it informally. For violent crimes, the likelihood of a case going to court varies substantially across police forces, with some prosecuting over 80% of cases and others diverting two thirds to other resolutions such as paying compensation. larger image | annotated R code to produce this chart

The government recently doubled the maximum sentence for assaulting a police officer to 12 months in prison, introducing a new offence of assaulting an emergency worker. So far, this change is associated with only small increases in sentences handed down in court. larger image | annotated R code to produce this chart Data source: Ministry of Justice, 2020 Notes To test whether there were any differences between imprisonment probability or sentence length before and after the new law was introduced, I ran separate ARIMA regression models (using the auto.

While Turkey has Europe’s highest imprisonment rate, England and Wales locks up more people per 100,000 population than any other western European country.

larger image | annotated R code to produce this chart

Data source: Eurostat, 2019 database tables crim_pris_cap.