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

      Total |
  Number of |
   Prenatal |
     Visits |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |        180        1.80        1.80
          1 |        234        2.34        4.14
          2 |        160        1.60        5.74
          3 |        225        2.25        7.99
          4 |        289        2.89       10.88
          5 |        368        3.68       14.56
          6 |        462        4.62       19.18
          7 |        486        4.86       24.04
          8 |        658        6.58       30.62
          9 |        612        6.12       36.74
         10 |      1,109       11.09       47.83
         11 |        812        8.12       55.95
         12 |      1,585       15.85       71.80
         13 |        724        7.24       79.04
         14 |        865        8.65       87.69
         15 |        513        5.13       92.82
         16 |        234        2.34       95.16
         17 |        104        1.04       96.20
         18 |         80        0.80       97.00
         19 |         38        0.38       97.38
         20 |         96        0.96       98.34
         21 |         15        0.15       98.49
         22 |         16        0.16       98.65
         23 |         13        0.13       98.78
         24 |         11        0.11       98.89
         25 |         16        0.16       99.05
         26 |          7        0.07       99.12
         27 |          1        0.01       99.13
         28 |          1        0.01       99.14
         29 |          3        0.03       99.17
         30 |          8        0.08       99.25
         35 |          1        0.01       99.26
         36 |          2        0.02       99.28
         40 |          1        0.01       99.29
         49 |          1        0.01       99.30
         99 |         70        0.70      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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