Frequencies for first 10,000 rows of nocharge variable in nhamcsed1993 dataset :

   expected |
  source of |
 payment-no |
     charge |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,877       98.77       98.77
          1 |        123        1.23      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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