Frequencies for first 10,000 rows of dfage variable in natl1997 dataset :

     Age of |
     Father |      Freq.     Percent        Cum.
------------+-----------------------------------
         13 |          1        0.01        0.01
         15 |          2        0.02        0.03
         16 |         15        0.15        0.18
         17 |         46        0.46        0.64
         18 |        117        1.17        1.81
         19 |        176        1.76        3.57
         20 |        216        2.16        5.73
         21 |        284        2.84        8.57
         22 |        326        3.26       11.83
         23 |        382        3.82       15.65
         24 |        390        3.90       19.55
         25 |        460        4.60       24.15
         26 |        435        4.35       28.50
         27 |        471        4.71       33.21
         28 |        433        4.33       37.54
         29 |        448        4.48       42.02
         30 |        449        4.49       46.51
         31 |        387        3.87       50.38
         32 |        392        3.92       54.30
         33 |        332        3.32       57.62
         34 |        312        3.12       60.74
         35 |        286        2.86       63.60
         36 |        230        2.30       65.90
         37 |        193        1.93       67.83
         38 |        147        1.47       69.30
         39 |        113        1.13       70.43
         40 |        106        1.06       71.49
         41 |         69        0.69       72.18
         42 |         54        0.54       72.72
         43 |         51        0.51       73.23
         44 |         41        0.41       73.64
         45 |         24        0.24       73.88
         46 |         21        0.21       74.09
         47 |         13        0.13       74.22
         48 |         15        0.15       74.37
         49 |         10        0.10       74.47
         50 |         12        0.12       74.59
         51 |         10        0.10       74.69
         52 |          8        0.08       74.77
         53 |          7        0.07       74.84
         54 |          5        0.05       74.89
         55 |          3        0.03       74.92
         56 |          1        0.01       74.93
         57 |          2        0.02       74.95
         58 |          3        0.03       74.98
         61 |          1        0.01       74.99
         63 |          1        0.01       75.00
         99 |      2,500       25.00      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 22 Dec 2015