Recent research from the Iowa Policy Project (IPP) takes a historical look at the rise and fall of union membership in America – and corresponding trends in income inequality.

IPP found when union membership was meager in the early 1900s, income inequality was stark – with nearly 40% of national income going to the top earners. But when union membership grew in the wake of the New Deal, income inequality decreased dramatically and the robust middle class of the 1940-70s was created.

This generation helped build the schools, infrastructure, economy, highways and programs that were critical to the American Dream – and that are now being eroded as income inequality reaches levels not seen since the Great Depression.

Watch this video to see the relationship between unions and shared prosperity:

[youtube=http://www.youtube.com/watch?v=QSYOedwIjMU]

Read more from EPI: Union decline and rising inequality in two charts