Frequencies for first 10,000 rows of nervous variable in natl1992 dataset :

      Other |
    central |
    nervous |
     system |
  anomalies |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |      9,997       99.97       99.97
          9 |          3        0.03      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 22 Dec 2015