Frequencies for year variable in ambulatory_surgical_measures_national dataset 

       Year |      Freq.     Percent        Cum.
------------+-----------------------------------
       2013 |          1       50.00       50.00
       2014 |          1       50.00      100.00
------------+-----------------------------------
      Total |          2      100.00

by Jean Roth , jroth@nber.org , 15 Nov 2016