Query: What percentage of the Miami population in 1970 was black?
Context: In 1960, non-Hispanic whites represented 80% of Miami-Dade county's population. In 1970, the Census Bureau reported Miami's population as 45.3% Hispanic, 32.9% non-Hispanic White, and 22.7% Black. Miami's explosive population growth has been driven by internal migration from other parts of the country, primarily up until the 1980s, as well as by immigration, primarily from the 1960s to the 1990s.