Union membership by US state

A good interactive graphic at NPR showing the change in union membership for each state from 1964 to 2014.

The overall rate has fallen from around a third to under 10%.

The three most unionised states today are New York on 25%, Alaska 23% and Hawaii 22%.

24 states have a union density of 10% to 20%.

16 states have a density of 5% to 10%.

Eight states have a union membership rate of under 5%, with the lowest being North Carolina at 2%.

The biggest declines over 50 years have been Michigan and Indiana which have both had 30% drops.

The only state to increase is Hawaii from 21.7% to 21.9%.

Would be interesting to explore why some states have declined so much, and others have not.