Police stop and search activity in Northern Ireland

In N.Ireland as in other parts of the UK the police have the right to conduct stop and search actions against people. Basically this means they can stop you in the street and search you. They do not have to arrest you. I was interested in investigating the number of stop and search activities carried out annually and how many of these actions result in arrests - an arrest may occur if they find something illegal. The data comes from here.

Raw data:

year        stop and search actions     arrests         %arrests/sands
2008-09  30047                                 1906            6.34
2009-10  53855                                 2150            3.99
2010-11  45394                                 1705             3.76
2011-12  35268                                 1705             4.83
2012-13  30502                                 1817             5.96
2013-14  32590                                 2199             6.75
2014-15  27539                                 2194             7.97
2015-16  34171                                 2391             7

The highest number of arrests resulting from stop and search activities was 2,199 in 2013-2014, but this was only 6.75% of the number of stop and search actions. This percentage never got above 8% and dropped below 4% on one occasion.  To investigate any possible correlation between stop and search actions and arrests I used R and ggplot.

the code:

> data <- read.csv('sands.csv', header=TRUE, sep=",")
> cor(data$sands, data$arrests)
[1] -0.08387308
> ggplot(data,aes(x=sands, y=arrests)) + geom_point(shape=1) + geom_smooth(method=lm, se=FALSE)

the correlation is very low suggesting that the number of arrests and the number of search actions have little connection. If any link exists it seems to be a negative relationship i.e. as the number of searches increased the number of arrests decreased. Graphically:

sands = stop and search actions

Summary:

While the police may state that stop and search is an important tool in their fight against crime the above figures do not suggest that it is very effective in arresting criminals (92% +) of people stopped are not arrested.