Frequencies for first 10,000 rows of dfage variable in natl1978 dataset :

     Age of |
     Father |      Freq.     Percent        Cum.
------------+-----------------------------------
         11 |          1        0.01        0.01
         15 |          1        0.01        0.02
         16 |          7        0.07        0.09
         17 |         48        0.48        0.57
         18 |        105        1.05        1.62
         19 |        222        2.22        3.84
         20 |        343        3.43        7.27
         21 |        425        4.25       11.52
         22 |        449        4.49       16.01
         23 |        553        5.53       21.54
         24 |        548        5.48       27.02
         25 |        580        5.80       32.82
         26 |        535        5.35       38.17
         27 |        499        4.99       43.16
         28 |        527        5.27       48.43
         29 |        485        4.85       53.28
         30 |        464        4.64       57.92
         31 |        380        3.80       61.72
         32 |        260        2.60       64.32
         33 |        229        2.29       66.61
         34 |        208        2.08       68.69
         35 |        189        1.89       70.58
         36 |        139        1.39       71.97
         37 |        113        1.13       73.10
         38 |         89        0.89       73.99
         39 |         62        0.62       74.61
         40 |         62        0.62       75.23
         41 |         49        0.49       75.72
         42 |         39        0.39       76.11
         43 |         35        0.35       76.46
         44 |         35        0.35       76.81
         45 |         18        0.18       76.99
         46 |         14        0.14       77.13
         47 |         12        0.12       77.25
         48 |         17        0.17       77.42
         49 |          9        0.09       77.51
         50 |         10        0.10       77.61
         51 |          4        0.04       77.65
         52 |          7        0.07       77.72
         53 |          6        0.06       77.78
         54 |          3        0.03       77.81
         55 |          5        0.05       77.86
         56 |          4        0.04       77.90
         57 |          3        0.03       77.93
         58 |          1        0.01       77.94
         59 |          1        0.01       77.95
         62 |          4        0.04       77.99
         70 |          3        0.03       78.02
         72 |          1        0.01       78.03
         99 |      2,197       21.97      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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