This is an interesting analysis and can only really be accurate if we assume the level of mapping and number of mappers in an area is the same from area to area

This is an interesting analysis and can only really be accurate if we assume the level of mapping and number of mappers in an area is the same from area to area. I don't think this is true. However, its possible statistics to find the number of mappers and the level of activity in an area from OSM, so a better analysis should normalise for this too. But! This only considers OSM from the point of view of a "hobby mapper" - the old school view of individuals going out with GPS units. Today a growing proportion mapping is contributed by governments, open data sets, batch imports, businesses and mapping teams, all of which vary by geography too.