Frequencies for first 10,000 rows of monprerflg variable in natl1972 dataset :

      Month |
   prenatal |
 care began |
 (by State) |
       flag |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,782       97.82       97.82
          1 |        218        2.18      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 3 Jan 2016