Frequencies for first 10,000 rows of monprerflg variable in natl1973 dataset :

      Month |
   prenatal |
 care began |
 (by State) |
       flag |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,720       97.20       97.20
          1 |        280        2.80      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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