Frequencies for first 10,000 rows of nprevis variable in natl1980 dataset :

      Total |
  Number of |
   Prenatal |
     Visits |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |        125        1.25        1.25
          1 |        122        1.22        2.47
          2 |        211        2.11        4.58
          3 |        259        2.59        7.17
          4 |        312        3.12       10.29
          5 |        394        3.94       14.23
          6 |        531        5.31       19.54
          7 |        588        5.88       25.42
          8 |        754        7.54       32.96
          9 |        772        7.72       40.68
         10 |      1,156       11.56       52.24
         11 |        756        7.56       59.80
         12 |      1,478       14.78       74.58
         13 |        756        7.56       82.14
         14 |        727        7.27       89.41
         15 |        444        4.44       93.85
         16 |        177        1.77       95.62
         17 |         78        0.78       96.40
         18 |         97        0.97       97.37
         19 |         23        0.23       97.60
         20 |         84        0.84       98.44
         21 |         15        0.15       98.59
         22 |          6        0.06       98.65
         23 |          3        0.03       98.68
         24 |          4        0.04       98.72
         25 |         12        0.12       98.84
         26 |          2        0.02       98.86
         27 |          2        0.02       98.88
         28 |          2        0.02       98.90
         29 |          2        0.02       98.92
         30 |          7        0.07       98.99
         36 |          2        0.02       99.01
         99 |         99        0.99      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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