Fig. 3. Change in the black population in New York City for 1970 to 1980. Changes of ≥ 2500 people refer to census tracts. The hatched and black areas are composed of many census tracts. This map shows that hundreds of thousands of people migrated within this single decade. The mini-census of 1975 indicated that most of the migration occurred between 1975 and 1980, with the exception of the South Bronx.