Frequencies for first 10,000 rows of prolong variable in natl1991 dataset :

  Prolonged |
      labor |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         38        0.38        0.38
          2 |      9,932       99.32       99.70
          9 |         30        0.30      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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