Frequencies for first 10,000 rows of forcep variable in linkco1991us_num dataset :

    Forceps |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        154        1.54        1.54
          2 |      9,702       97.02       98.56
          9 |        144        1.44      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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