Stop and search vs. possession of drugs offences

Stop and search is highly correlated (0.93 Pearson coefficient) with the fall in prosecutions for possession of Class A, B and C drugs. Should we increase the use of stop and search, reduced it or leave it as it is? 

Police stop and search powers are an effective means of detecting drug possession. In the decade between 2009 and 2018, the number of stop and searches decreased by 69% from 1,177,327 to 370,454. Over the same time period the number of prosecutions for drug possession offences fell from 38,913 to 24,499. These two statistics are highly correlated, with a Pearson correlation coefficient of 0.93 (anything above 0.50 is considered a high correlation). Although correlation is not causation, the causal link between the two statistics is clear.

Use of stop and search is increasing after a 10-year minimum in 2017. A lag between possession prosecutions and stop and search is likely, so if the increase in stop and search continues, we would expect to see more prosecutions for drug possession in the future.