Which heading should replace the question mark in the chart below?

year

?

1918

1.4

1919

1.4

1920

5.2

1921

11.7

unemployment rate in percent

immigration from asia in millions

immigration from europe in millions

women in the workforce in percent

the  seven  days  battles  were  a series of seven battles over seven  days from june 25 to july 1, 1862, near richmond, virginia,  during  the american civil war. the  seven  days ended with mcclellan's army in relative safety next to the james river, having suffered almost 16,000 casualtiesduring  the retreat.

social contract theory, nearly as old as philosophy itself, is the view that persons' moral and/or political obligations are dependent upon a contract or agreement among them to form the society in which they liv