Do the Indian and Bangladeshi communities have different customs regarding surnames that would lead to a more homogenous naming. Because the results seem disproportionate and shrink massively if you move the slider to the 2nd most popular name or further.
See if you can spot the Cohen island in N-NW London. I lived in that area for a bit, and around Golders Green and Stamford Hill there's a large Jewish community, many of them orthodox.
This beautifully illustrates Thomas Schelling's racial segregation model, for which he coined the term "Tipping Point" 30 years before Malcolm Gladwell popularized it:<p>Schelling, T. (1969). Models of segregation. The American Economic Review, 59(2), 488-493<p>(Schelling won the Nobel Prize in economics in 2005)
Is there any significance to the distribution of the "Welsh" names? They appear a bit more central, but not especially. Perhaps at one time they were the poorer, more centrally located 'immigrants', but have since spread out?