Frequencies for first 10,000 rows of proc variable in nhamcsed2006 dataset :

       were |
 procedures |
  provided? |      Freq.     Percent        Cum.
------------+-----------------------------------
         no |      4,888       48.88       48.88
        yes |      4,560       45.60       94.48
  no answer |        552        5.52      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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