Final answer:
Discriminatory practices and economic opportunities are external factors fostering segregation. Redlining and restrictive property covenants historically confined minorities, while economic activities among cohesive minority groups can lead to self-segregation, despite persistent discrimination.
Step-by-step explanation:
Some external factors that encourage ethnic minorities to opt for segregation in cities include discriminatory practices and economic opportunities. Discriminatory practices, such as redlining and restrictive covenants, have historically prevented minorities from living in certain areas, fostering segregation. For instance, in northern cities, neighborhoods remain segregated due to such past practices. Economic opportunities can also lead to segregation, where cohesive minority group activities can lead to self-segregation within certain industries or neighborhoods. Even though market forces can provide certain freedoms, they alone are unlikely to eliminate discrimination against groups like African Americans, which have continued even after significant legal changes, like the Civil Rights Act of 1964.