Frequencies for first 10,000 rows of mage12 variable in natl1981 dataset :

     Age of |
     Mother |
  recode 12 |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         44        0.44        0.44
          3 |        124        1.24        1.68
          4 |        290        2.90        4.58
          5 |        411        4.11        8.69
          6 |        529        5.29       13.98
          7 |        637        6.37       20.35
          8 |      3,537       35.37       55.72
          9 |      2,817       28.17       83.89
         10 |      1,215       12.15       96.04
         11 |        326        3.26       99.30
         12 |         63        0.63       99.93
         13 |          7        0.07      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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