Frequencies for first 10,000 rows of mage12 variable in natl1970 dataset :

     Age of |
     Mother |
  recode 12 |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         57        0.57        0.57
          3 |        150        1.50        2.07
          4 |        303        3.03        5.10
          5 |        457        4.57        9.67
          6 |        657        6.57       16.24
          7 |        779        7.79       24.03
          8 |      3,790       37.90       61.93
          9 |      2,200       22.00       83.93
         10 |        980        9.80       93.73
         11 |        479        4.79       98.52
         12 |        139        1.39       99.91
         13 |          9        0.09      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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