Frequencies for first 10,000 rows of nprev12 variable in natl1987 dataset :

  Number of |
   Prenatal |
     Visits |
     Recode |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        213        2.13        2.13
          2 |        211        2.11        4.24
          3 |        395        3.95        8.19
          4 |        684        6.84       15.03
          5 |      1,004       10.04       25.07
          6 |      1,725       17.25       42.32
          7 |      2,960       29.60       71.92
          8 |      1,452       14.52       86.44
          9 |        749        7.49       93.93
         10 |        225        2.25       96.18
         11 |        229        2.29       98.47
         12 |        153        1.53      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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