Frequencies for first 10,000 rows of paydk variable in nhamcsed2005 dataset :

    unknown |
  source of |
    payment |      Freq.     Percent        Cum.
------------+-----------------------------------
         no |      9,633       96.33       96.33
        yes |        367        3.67      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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