Frequencies for first 10,000 rows of proc variable in nhamcsed2012 dataset :

Were procedures provided at this visit? |      Freq.     Percent        Cum.
----------------------------------------+-----------------------------------
                                     No |      5,121       51.21       51.21
                                    Yes |      4,560       45.60       96.81
Entire item blank, including 'None' box |        319        3.19      100.00
----------------------------------------+-----------------------------------
                                  Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 7 Nov 2016