For my own edification, today I downloaded past Dow Jones Industrial Average data from 1928 to present, and took a look-see just to see what the past trends were, and how bad things right now really are.
I was looking at the data, and noticed curious four year cycles in the market that appeared to be tied to presidential elections. The pattern becomes especially clear if you look at the percentage change in the DJIA from what it was two years previously. Below is a plot of that versus time, with the superimposed vertical bars showing the year that a new president started his term. Note that for every single president since the 1950's, the market tanked within the first year or so of him first taking office, followed by a rally that peaked usually a couple of years before his term ended (the only exception is start of Johnson's term who, when he started, wasn't elected). In fact, the beginning of each of the terms transects rather well the distance between the peak of the rally and the valley of the downturn.
For presidents who served two 4 year terms, there even appears to be economic downturn during their re-election year (the notable exception being Clinton).
It would appear that the American economy does not like the uncertainty that elections and new presidents bring, and the economic downturn centered around the election of new presidents is very predictable. The fact that the economy doesn't recover until a year or so into the start of a new presidential term is bad news because it means that we are very likely going to see the DJIA drop significantly more over the next 12 to 18 months, in a manner only rivaled by the Great Depression.
Update: I just poked around on the internet, and apparently I'm not the first to notice this. See here for instance. Makes me wonder why the droves of economic pundits on the news programs lately don't mention this...