Frequencies for first 10,000 rows of forcep variable in natl1990 dataset :

    Forceps |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      1,220       12.20       12.20
          2 |      8,773       87.73       99.93
          9 |          7        0.07      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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