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

      Total |
  Number of |
   Prenatal |
     Visits |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |        213        2.13        2.13
          1 |         89        0.89        3.02
          2 |        122        1.22        4.24
          3 |        168        1.68        5.92
          4 |        227        2.27        8.19
          5 |        312        3.12       11.31
          6 |        372        3.72       15.03
          7 |        438        4.38       19.41
          8 |        566        5.66       25.07
          9 |        622        6.22       31.29
         10 |      1,103       11.03       42.32
         11 |        852        8.52       50.84
         12 |      2,108       21.08       71.92
         13 |        687        6.87       78.79
         14 |        765        7.65       86.44
         15 |        531        5.31       91.75
         16 |        218        2.18       93.93
         17 |         95        0.95       94.88
         18 |        130        1.30       96.18
         19 |         20        0.20       96.38
         20 |        114        1.14       97.52
         21 |         14        0.14       97.66
         22 |         10        0.10       97.76
         23 |          7        0.07       97.83
         24 |         14        0.14       97.97
         25 |         17        0.17       98.14
         26 |          5        0.05       98.19
         27 |          3        0.03       98.22
         28 |          1        0.01       98.23
         29 |          1        0.01       98.24
         30 |         13        0.13       98.37
         32 |          1        0.01       98.38
         34 |          1        0.01       98.39
         37 |          1        0.01       98.40
         40 |          5        0.05       98.45
         49 |          2        0.02       98.47
         99 |        153        1.53      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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