Frequencies for first 10,000 rows of nochron variable in nhamcsed2013 dataset :

   Does patient have: None of the above |      Freq.     Percent        Cum.
----------------------------------------+-----------------------------------
                                     No |      1,868       18.68       18.68
                                    Yes |      7,902       79.02       97.70
Entire item blank, including 'None' box |        230        2.30      100.00
----------------------------------------+-----------------------------------
                                  Total |     10,000      100.00

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