See also:
http://www.marketwatch.com/investing/index/dxy/charts?symb=DXY&countrycode=US&time=13&startdate=1%2F4%2F1999&enddate=9%2F20%2F2014&freq=1&compidx=none&compind=none&comptemptext=Enter+Symbol%28s%29&comp=none&uf=7168&ma=1&maval=50&lf=1&lf2=4&lf3=0&type=2&size=2&style=1013

It’s been very much tied to risk appetite and QE. Also stocks.

Dollar went astronomical after Aug 2008, only to drop hard when QE(1) was announced.

Rise in DXY in early-2010 was followed by a drop in DOW below 10,000 in mid-2010. Rise of DXY in early 2011 was concurrent with a drop in DOW to the low 11,000 range. 2012 peak in DXY, DOW hiccuped in April-June.

Like it or not, dollar strength has been pretty much inversely tied to risk appetite since 2008. Historically, this hasn’t been true, but the last few years have been different.