Why Does Economy Do Better Under Democrats?

That the correlation exists is not debatable.

http://www.amazon.com/Theyre-Not-Even-Close-Democratic/dp/1880026090/ref=sr_1_1?ie=UTF8&qid=1446470971&sr=8-1&keywords=not+even+close

To be sure a basic fact of economics is correlation doesn't prove causation.

Even so, what are the chances that such a strong correlation is purely coincidental?

So let's hear from an actual economist-Paul Krugman:

"Last week The Wall Street Journal published an op-ed article by Carly Fiorina titled “Hillary Clinton Flunks Economics,” ridiculing Mrs. Clinton’s assertions that the U.S. economy does better under Democrats. “America,” declared Ms. Fiorina, “needs someone in the White House who actually knows how the economy works.”

"Well, we can agree on that much."

"Partisan positioning on the economy is actually quite strange. Republicans talk about economic growth all the time. They attack Democrats for “job-killing” government regulations, they promise great things if elected, they predicate their tax plans on the assumption that growth will soar and raise revenues. Democrats are far more cautious. Yet Mrs. Clinton is completely right about the record: historically, the economy has indeed done better under Democrats."

http://www.nytimes.com/2015/11/02/opinion/partisan-growth-gaps.html?ref=opinion&_r=0

I think that's already a tell. The fact that Democrats are far more cautious. That's already more in line with how economists actually think. The GOP is infamous for making wild promises. 

Jeb is running on achieving 4% GDP. How did he come by this number? Just because it sounded good in a rap session. Wish I was kidding. 

Huckabee then one upped Jeb by promising 6% GDP. It's easy to run as a GOP Presidential candidate.

http://lastmenandovermen.blogspot.com/2015/08/move-over-jeb-mike-huckabee-promises-6.html

 Watch me get in: GOPers make me your nominee. Jeb will just give you 4% growth and Huck 6%.

I promise if elected I will give you 8% GDP. That and and impeach HIllary Clinton. Ok the liberal media says that makes no sense. Ignore them!

As Krugman goes on to say, we don't know for sure why the Dems have this advantage. It could just be luck. In truth the President is always given too much credit or blame for the economy. 

"Hence the asymmetry between the parties. Democrats can afford to be cautious in their economic promises precisely because their policies can be sold on their merits. Republicans must sell an essentially unpopular agenda by confidently declaring that they have the ultimate recipe for prosperity — and hope that nobody points out their historically poor track record."