So what you're saying is that under FDR's policies unemployment was cut nearly in half in 8 years. 

Sure beats what the previous Republican Administration did, which was run unemployment up from about 4% to 25%.

Reducing the unemployment rate from 25% to 14% wasn't an insignificant economic feat-- a fact which the people who actually lived through the depression seemed to understand, as they sent FDR back to the White House for so many terms that we felt we had to pass a Constitutional Amendment to term-limit the presidency, just so other people would get a chance at the oval office ;-)

But that's pretty typical of the economy, and the employment rate-- they take the stairs up, and the elevator down.  That's probably because people get hired one at a time, and laid off by the thousands at once.  In general, things are destroyed faster than they are built.

You can find all kinds of opinions and studies about FDR's policies.  And I know this will be shocking to you, but some folks even actually have political axes to grind against FDR!  Bottom line, you've given me no reason why I should treat this particular study as the gospel truth.