2. Things you need to know

What the data measures

This data measures the number of arrests for 'notifiable offences' – offences for which the police must complete a crime report.

Rates of arrest per 1,000 people are rounded to the nearest whole number. Percentages of arrests in age groups are rounded to one decimal place.

Not included in the data

Lancashire police force is excluded as they were unable to provide arrests data.

The City of London police force area has been excluded due to the small number of people living in the area compared with those who visit.

How arrest rates are calculated

The arrest rate is the number of people arrested from a particular ethnic group out of every 1,000 people from the same group.

A person arrested in a particular area may not necessarily live in that area. Population estimates for police force areas are based on permanent residents of that area as reported in the 2011 Census. Read more about problems using Census data to work out rates.

We use ‘relative likelihoods’ in the data to make comparisons, for example ‘Black people were over 3 times as likely to be arrested as White people’. You can read more about using relative likelihoods to compare ethnic disparities.

The ethnic groups used in the data

The data uses the 5 ethnic groups from the 2001 Census.

The person arrested states their ethnicity at the time of arrest. If someone doesn’t give their ethnicity, it’s shown as ‘unknown’ in the tables.

In the 13 years to March 2019, the percentage of people arrested whose ethnicity wasn't known ranged from 2% to 12%.

Methodology

A person arrested for a notifiable offence is counted for each time they are arrested, as long as the offence is not related to an offence that happened earlier in the same financial year (April to March).

If it is connected, or if a person has been arrested for more than one notifiable offence on the same occasion, the offence with the highest maximum penalty is recorded.

Someone who is arrested is usually asked for their ethnicity. The circumstances of an arrest may affect the accuracy of this information.

There are 43 police force areas in England and Wales. Data from April 2017 to March 2019 is from 42 police forces. Data from April 2006 to March 2017 is from all 43 police forces.

In the data file

See download the data for the number of arrests by area and ethnicity.