Why is the US economy so unapologetically partisan? Do the laws of supply and demand have a liberal bias? Are Democrats better at governing for growth? Do these graphs prove something fundamental about the superiority of Keynesianism? Maybe none of the above. Blinder and Watson propose that the answer has less to do with policies -- taxing, spending, redistributing -- and more to do with dumb luck. "The Democratic edge stems mainly from more benign oil shocks, superior [productivity growth], a more favorable international environment, and perhaps more optimistic consumer expectations about the near-term future," they wrote.
For one, the authors note that their four preferred factors -- oil shocks, productivity growth, international conditions, and consumer expectations -- still only explain about half the difference in growth rates. "The rest remains, for now, a mystery of the still mostly-unexplored continent," Blinder and Watson write. "The word 'research,' taken literally, means search again. We invite other researchers to do so." As noted above, it's also not clear how much policy can influence the factors they call "luck" -- things like oil shocks or productivity growth or consumer expectations. Perhaps these are things that presidents can have a lot of influence over. Or perhaps these are factors they can only affect at the margins. Figuring that out wouldn't just be worthwhile for purposes of bragging rights -- it'd be useful to know if there are policies that really can produce such a consistent and large boost to economic growth.