Frequencies for first 10,000 rows of monprec variable in natl1983 dataset :

     Detail |
      Month |
   Prenatal |
 Care began |      Freq.     Percent        Cum.
------------+-----------------------------------
          - |         54        0.54        0.54
          0 |        180        1.80        2.34
          1 |      1,105       11.05       13.39
          2 |      3,726       37.26       50.65
          3 |      2,211       22.11       72.76
          4 |      1,089       10.89       83.65
          5 |        699        6.99       90.64
          6 |        426        4.26       94.90
          7 |        262        2.62       97.52
          8 |        176        1.76       99.28
          9 |         72        0.72      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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