Frequencies for first 10,000 rows of ume_primc variable in linkpe2009psden dataset :

    Primary |
  C-Section |
        U;R |
(f_u_primac |
  rep flag) |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        481        4.81        4.81
          2 |      2,889       28.89       33.70
          9 |         52        0.52       34.22
          . |      6,578       65.78      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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