In talking of austerity Krugman neglects monetary policy[1] ("The key measure you want to look at is the ratio of debt to G.D.P." [2]), yet that chart you reference is inflation-adjusted 2009 dollars. That is to say, it is an apples to oranges comparison if we are going to talk of Krugman's version of austerity.

[1] http://www.forbes.com/sites/realspin/2015/03/12/the-austerit...

[2] http://www.nytimes.com/2013/05/06/opinion/krugman-the-chutzp...