Frequencies for first 10,000 rows of ca_mnsb variable in natlterr2014 dataset :

Meningomyel |
    ocele / |
      Spina |
   Bifida Y |
        Yes |      Freq.     Percent        Cum.
------------+-----------------------------------
            |      1,077       10.77       10.77
          N |      8,811       88.11       98.88
          U |        110        1.10       99.98
          Y |          2        0.02      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 15 Jun 2016