Mapping suicide in London: A brief methodological case study on the application of the smoothing technique

Background: When one intends to globally smooth unstable rates, e.g., suicide rates in a region, one needs to consider whether it is better to smooth the rates toward the global mean of the country or toward the global mean of the same region. Aims: The present study aims to provide a methodological framework to answer this question by smoothing suicide rates within London boroughs. Methods: Based on the results of the spatial autocorrelation statistics, the noniterative empirical Bayes method of moments was chosen to globally smooth the suicide rate of each borough, first toward the global mean of England and Wales, and second toward the mean of the London region. Results: The results revealed that smoothing the suicide rates of the boroughs toward the global mean of England and Wales had a stronger influence in reducing the variability of suicide rates than smoothing toward the global mean of the London region. Conclusions: Smoothing the rates toward the mean of a region within a country acts somewhat between global and local smoothing.