Frequencies for first 10,000 rows of dfage variable in natl1972 dataset :

     Age of |
     Father |      Freq.     Percent        Cum.
------------+-----------------------------------
         15 |          3        0.03        0.03
         16 |          7        0.07        0.10
         17 |         59        0.59        0.69
         18 |        158        1.58        2.27
         19 |        332        3.32        5.59
         20 |        386        3.86        9.45
         21 |        493        4.93       14.38
         22 |        574        5.74       20.12
         23 |        636        6.36       26.48
         24 |        676        6.76       33.24
         25 |        640        6.40       39.64
         26 |        513        5.13       44.77
         27 |        482        4.82       49.59
         28 |        484        4.84       54.43
         29 |        408        4.08       58.51
         30 |        378        3.78       62.29
         31 |        263        2.63       64.92
         32 |        263        2.63       67.55
         33 |        219        2.19       69.74
         34 |        185        1.85       71.59
         35 |        154        1.54       73.13
         36 |        161        1.61       74.74
         37 |        114        1.14       75.88
         38 |         98        0.98       76.86
         39 |         91        0.91       77.77
         40 |         77        0.77       78.54
         41 |         63        0.63       79.17
         42 |         68        0.68       79.85
         43 |         41        0.41       80.26
         44 |         45        0.45       80.71
         45 |         37        0.37       81.08
         46 |         23        0.23       81.31
         47 |         15        0.15       81.46
         48 |         17        0.17       81.63
         49 |         15        0.15       81.78
         50 |         17        0.17       81.95
         51 |          5        0.05       82.00
         52 |         11        0.11       82.11
         53 |          4        0.04       82.15
         54 |          4        0.04       82.19
         55 |          8        0.08       82.27
         56 |          4        0.04       82.31
         57 |          2        0.02       82.33
         58 |          4        0.04       82.37
         60 |          5        0.05       82.42
         61 |          2        0.02       82.44
         62 |          2        0.02       82.46
         63 |          1        0.01       82.47
         64 |          2        0.02       82.49
         70 |          1        0.01       82.50
         71 |          1        0.01       82.51
         73 |          1        0.01       82.52
         99 |      1,748       17.48      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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