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

   Abruptio |
   placenta |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        414        4.14        4.14
          2 |      9,379       93.79       97.93
          9 |        207        2.07      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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