Frequencies for first 10,000 rows of mage12 variable in natl1977 dataset :

     Age of |
     Mother |
  recode 12 |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         89        0.89        0.89
          3 |        158        1.58        2.47
          4 |        373        3.73        6.20
          5 |        526        5.26       11.46
          6 |        599        5.99       17.45
          7 |        771        7.71       25.16
          8 |      3,569       35.69       60.85
          9 |      2,505       25.05       85.90
         10 |        985        9.85       95.75
         11 |        330        3.30       99.05
         12 |         91        0.91       99.96
         13 |          4        0.04      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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