Frequencies for first 10,000 rows of proc variable in nhamcsed2005 dataset :

       were |
 procedures |
  provided? |      Freq.     Percent        Cum.
------------+-----------------------------------
         no |      4,364       43.64       43.64
        yes |      4,957       49.57       93.21
  no answer |        679        6.79      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 28 Mar 2016