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

    Forceps |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      1,254       12.54       12.54
          2 |      8,687       86.87       99.41
          9 |         59        0.59      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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