Frequencies for first 10,000 rows of microce variable in natl1990 dataset :

Microcephal |
         us |      Freq.     Percent        Cum.
------------+-----------------------------------
          2 |      9,938       99.38       99.38
          9 |         62        0.62      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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