Frequencies for first 10,000 rows of proc variable in nhamcsed1996 dataset :

       were |
 procedures |
  provided? |      Freq.     Percent        Cum.
------------+-----------------------------------
        Yes |      4,337       43.37       43.37
  No answer |      5,663       56.63      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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