Frequencies for first 10,000 rows of monprec variable in natl1986 dataset :

     Detail |
      Month |
   Prenatal |
 Care began |      Freq.     Percent        Cum.
------------+-----------------------------------
          - |        121        1.21        1.21
          0 |        214        2.14        3.35
          1 |      1,252       12.52       15.87
          2 |      3,820       38.20       54.07
          3 |      2,054       20.54       74.61
          4 |        996        9.96       84.57
          5 |        639        6.39       90.96
          6 |        408        4.08       95.04
          7 |        276        2.76       97.80
          8 |        154        1.54       99.34
          9 |         66        0.66      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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