Frequencies for first 10,000 rows of monprec variable in natl1988 dataset :

     Detail |
      Month |
   Prenatal |
 Care began |      Freq.     Percent        Cum.
------------+-----------------------------------
          - |         80        0.80        0.80
          0 |        206        2.06        2.86
          1 |      1,450       14.50       17.36
          2 |      3,773       37.73       55.09
          3 |      1,904       19.04       74.13
          4 |      1,034       10.34       84.47
          5 |        676        6.76       91.23
          6 |        406        4.06       95.29
          7 |        266        2.66       97.95
          8 |        141        1.41       99.36
          9 |         64        0.64      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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