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

  Prolonged |
 labor (>20 |
     hours) |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         69        0.69        0.69
          2 |      9,724       97.24       97.93
          9 |        207        2.07      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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