The problem of retention within Islam explained by how a convert is perceived within the Uma. The retention rate of converts is around 20 - 25% meaning 75 - 80% leave.
For years, since 2015, many some ex-Muslims who have warred the western countries of the nastiness of these Muslim men which is the outward sign of the consanguinitation of their minds towards western women. In that broken mind they will commit more crime.