Frequencies for first 10,000 rows of therprev variable in namcs2000 dataset :

       were |
  ther/prev |
   services |
ordered/pro |
     vided? |      Freq.     Percent        Cum.
------------+-----------------------------------
         No |      6,458       64.58       64.58
        Yes |      3,253       32.53       97.11
  No answer |        289        2.89      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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