Frequencies for first 10,000 rows of gestestm variable in natl2001 dataset :

   Clinical |
Estimate of |
  Gestation |
  Used Flag |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        486        4.86        4.86
          . |      9,514       95.14      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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