Frequencies for first 10,000 rows of tocol variable in natl1993 dataset :

  Tocolysis |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         75        0.75        0.75
          2 |      9,895       98.95       99.70
          9 |         30        0.30      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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