Frequencies for first 10,000 rows of forcep variable in natl1992 dataset :

    Forceps |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        877        8.77        8.77
          2 |      9,119       91.19       99.96
          9 |          4        0.04      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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