Complex sentence: Out of 3 other surrounding neighborhoods, Mattapan saw a population decrease but has the highest proportion of Black/African American residents in the city, but the number of blacks actually dropped over the last decade.
Split into simpler sentences: Out of 3 other surrounding neighborhoods, Mattapan saw a population decrease. Mattapan has the highest proportion of Black/African American residents in the city, but the number of blacks actually dropped over the last decade.