Frequencies for first 10,000 rows of monprec variable in natl1978 dataset :

     Detail |
      Month |
   Prenatal |
 Care began |      Freq.     Percent        Cum.
------------+-----------------------------------
          - |         76        0.76        0.76
          0 |        124        1.24        2.00
          1 |        867        8.67       10.67
          2 |      3,649       36.49       47.16
          3 |      2,402       24.02       71.18
          4 |      1,211       12.11       83.29
          5 |        658        6.58       89.87
          6 |        440        4.40       94.27
          7 |        332        3.32       97.59
          8 |        189        1.89       99.48
          9 |         52        0.52      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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