Frequencies for first 10,000 rows of preplace variable in natlterr1995 dataset :

   Placenta |
     previa |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         34        0.34        0.34
          2 |      9,952       99.52       99.86
          9 |         14        0.14      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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