Declining Trend in GDP Growth Post WWII Recessions

Bespokeinvest.com came out with a post recently calling the current economy "Obamalocks" since its featuring subpar growth with accomodative fed policies.  I don't quite agree with their explanation but its interesting to look at the data they accumulated.  



As you can see from their chart, the current 2009 recession recovery has been relatively weak.  They have some inaccuracies/inconsistency in their number, one example is that they counted median without 2009 numbers but counted average with 2009 numbers.  I didn't check if their GDP numbers are accurate but one thing that struck to me is if you look at the increasing red trend.  If you average out the GDP numbers for each recession and plot it by date, you'll find something interesting.

Notice the very obvious trend where the GDP growth trend after every recession post WWII is progressively getting worse.  The only big outlier is the 1958 recession which was much lower but this may be more of a definition.  If you look at the tablet above from Bespoke, they included several negative GDP values about 3 years after the recession.  So in essence 1958 had a slight double dip recession effect in its average.  If you take that double dip value out, you'll find a much better fit.  While thats questionable from a methodology standpoint, its still interesting to see the long term trend.

Data excluding "double dip" effect from 1958 recession

So what's responsible for this slowdown in GDP recovery trend?  I have some theories but not sure.  Will have to look into it some more.