What demographic shift caused the african american population of harlem to grow rapidly in the early-1920s?

The correct answer is The Great Migration.

During the early 1920's, many African Americans moved from states in the deep South (like Georgia, South Carolina, etc.) to cities in the North. Many factors contributed to this move including: availability of factory jobs in major cities like New York, less frequent and violent instances against African Americans in comparison to the South, and ability to express ones talents.

This migration to the North helped to start the Harlem Renaissance. This revival of African American culture resulted in the growth of jazz music and poetry written by African American artists.

the correct answer is:   "   3.6 % " .

          →   the unemployment rate is:   " 3.6 % " .

explanation:

to calculate the "unemployment rate" :

the "unemployment rate"   =

  [# of people unemployed] /   [working age population]   * 100 %   ;

                =   [9 million] / [250 million]     *   100 % ;

    →     note:   the units of "million" cancel out;

                    since:   " {million} / {million} = 1 " ;

                =   (9 / 250)   * 100 %   ;

                = 0.036 * 100 % ;

                =   3.6 %

answer:   the unemployment rate is:   " 3.6 % " .