Frequencies for first 10,000 rows of monprec variable in natl1987 dataset :

     Detail |
      Month |
   Prenatal |
 Care began |      Freq.     Percent        Cum.
------------+-----------------------------------
          - |         96        0.96        0.96
          0 |        213        2.13        3.09
          1 |      1,446       14.46       17.55
          2 |      3,780       37.80       55.35
          3 |      1,967       19.67       75.02
          4 |      1,030       10.30       85.32
          5 |        686        6.86       92.18
          6 |        330        3.30       95.48
          7 |        248        2.48       97.96
          8 |        140        1.40       99.36
          9 |         64        0.64      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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