In my view this happens everwhere , most people like to be with their "own kind" there are a small spanish, italian and ukrainian communities here in manchester as well as jewish , catholic and irish catholic communities ,while there are no streets where 70% or 80% of people are from certain backgrounds , 20% or 30% is much more common , many will not leave these settlement areas because they enjoy living with neigbours of their own kind .
You really cannot legislate for this and if someone likes living with their own kind they will do it