Frequencies for first 10,000 rows of nprevis variable in natl1985 dataset :

      Total |
  Number of |
   Prenatal |
     Visits |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |        158        1.58        1.58
          1 |         96        0.96        2.54
          2 |        161        1.61        4.15
          3 |        205        2.05        6.20
          4 |        242        2.42        8.62
          5 |        355        3.55       12.17
          6 |        424        4.24       16.41
          7 |        450        4.50       20.91
          8 |        632        6.32       27.23
          9 |        618        6.18       33.41
         10 |      1,162       11.62       45.03
         11 |        881        8.81       53.84
         12 |      1,674       16.74       70.58
         13 |        778        7.78       78.36
         14 |        875        8.75       87.11
         15 |        550        5.50       92.61
         16 |        237        2.37       94.98
         17 |        105        1.05       96.03
         18 |         89        0.89       96.92
         19 |         48        0.48       97.40
         20 |         90        0.90       98.30
         21 |         25        0.25       98.55
         22 |         11        0.11       98.66
         23 |         14        0.14       98.80
         24 |          9        0.09       98.89
         25 |         11        0.11       99.00
         26 |          5        0.05       99.05
         27 |          3        0.03       99.08
         28 |          1        0.01       99.09
         30 |          7        0.07       99.16
         31 |          1        0.01       99.17
         36 |          1        0.01       99.18
         40 |          1        0.01       99.19
         99 |         81        0.81      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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