Frequencies for first 10,000 rows of stimula variable in natl1991 dataset :

Stimulation |
   of labor |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        871        8.71        8.71
          2 |      9,117       91.17       99.88
          9 |         12        0.12      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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