Frequencies for first 10,000 rows of nopay variable in nhamcsed2012 dataset :

No answer to expected source of payment |
                                   item |      Freq.     Percent        Cum.
----------------------------------------+-----------------------------------
At least one source of payment is recor |      9,861       98.61       98.61
       All sources of payment are blank |        139        1.39      100.00
----------------------------------------+-----------------------------------
                                  Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 7 Nov 2016