The distribution of occupation in Britain, 1981, after binomial smoothing (Colour).

Three colour mixing of 129,211 census enumeration districts smoothed by ten passes of a binomial filter on an equal population cartogram software by author on an Archimedes computer.

Here the image is, perhaps, made clearer by smoothing. In places the blue and yellow colours have run into each other and produced a green which does not reflect reality. In central London the algorithm has failed along the cliff between the most and least prosperous places, so here it is shown as a white ring around a blue core. The filter works best where the underlying pattern is most amenable to being smoothed.