Frequencies for first 10,000 rows of mage12 variable in natl1980 dataset :

     Age of |
     Mother |
  recode 12 |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         62        0.62        0.62
          3 |        144        1.44        2.06
          4 |        268        2.68        4.74
          5 |        465        4.65        9.39
          6 |        541        5.41       14.80
          7 |        638        6.38       21.18
          8 |      3,590       35.90       57.08
          9 |      2,680       26.80       83.88
         10 |      1,207       12.07       95.95
         11 |        339        3.39       99.34
         12 |         61        0.61       99.95
         13 |          5        0.05      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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