12  See Edward P. Lazear and James R. Spletzer (2012), “The United States Labor Market: Status Quo or a New Normal?” NBER Working Paper Series 18386 (Cambridge, Mass. : National Bureau of Economic Research, September). See also Ayșegül Șahin, Joseph Song, Giorgio Topa, and Giovanni L. Violante (2012), “Mismatch Unemployment”, NBER Working Paper Series 18265 (Cambridge, Mass.
: National Bureau of Economic Research, August). 13  See Jesse Rothstein (2012), “The Labor Market Four Years into the Crisis: Assessing Structural Explanations”, Industrial and Labor Relations Review, vol. 65 (July), pp. 467–500.