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

   Does patient have: None of the above |      Freq.     Percent        Cum.
----------------------------------------+-----------------------------------
                                     No |      1,717       17.17       17.17
                                    Yes |      7,477       74.77       91.94
Entire item blank, including 'None' box |        806        8.06      100.00
----------------------------------------+-----------------------------------
                                  Total |     10,000      100.00

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