Frequencies for first 10,000 rows of paydk variable in nhamcsed2008 dataset :

    unknown |
  source of |
    payment |      Freq.     Percent        Cum.
------------+-----------------------------------
         no |      9,716       97.16       97.16
        yes |        284        2.84      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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