I find their evidence that a recession accompanied by a financial crisis is likely to be much more serious than an ordinary recession persuasive, but the point remains contentious. Even in the case of the Great Recession, it is possible that the U.S. recession got a second wind when the euro-zone crisis worsened in 2011.
But no one should forget the immensity of the financial crisis that the U.S. economy and the world went through following the bankruptcy of Lehman Brothers – and no one should forget that such things could happen again.