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

    Primary |
  C-section |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      1,588       15.88       15.88
          2 |      8,405       84.05       99.93
          9 |          7        0.07      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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