Frequencies for first 10,000 rows of tocol variable in natl1989 dataset :

  Tocolysis |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         87        0.87        0.87
          2 |      9,859       98.59       99.46
          9 |         54        0.54      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 3 Jan 2016