Frequencies for first 10,000 rows of dfage variable in natl1975 dataset :

     Age of |
     Father |      Freq.     Percent        Cum.
------------+-----------------------------------
         15 |          2        0.02        0.02
         16 |          6        0.06        0.08
         17 |         62        0.62        0.70
         18 |        153        1.53        2.23
         19 |        282        2.82        5.05
         20 |        392        3.92        8.97
         21 |        518        5.18       14.15
         22 |        513        5.13       19.28
         23 |        528        5.28       24.56
         24 |        623        6.23       30.79
         25 |        610        6.10       36.89
         26 |        584        5.84       42.73
         27 |        614        6.14       48.87
         28 |        540        5.40       54.27
         29 |        365        3.65       57.92
         30 |        388        3.88       61.80
         31 |        331        3.31       65.11
         32 |        248        2.48       67.59
         33 |        196        1.96       69.55
         34 |        169        1.69       71.24
         35 |        140        1.40       72.64
         36 |        119        1.19       73.83
         37 |        102        1.02       74.85
         38 |         86        0.86       75.71
         39 |         71        0.71       76.42
         40 |         62        0.62       77.04
         41 |         53        0.53       77.57
         42 |         51        0.51       78.08
         43 |         36        0.36       78.44
         44 |         35        0.35       78.79
         45 |         17        0.17       78.96
         46 |         18        0.18       79.14
         47 |         19        0.19       79.33
         48 |         12        0.12       79.45
         49 |         17        0.17       79.62
         50 |         10        0.10       79.72
         51 |          5        0.05       79.77
         52 |          6        0.06       79.83
         53 |          6        0.06       79.89
         54 |          5        0.05       79.94
         55 |          6        0.06       80.00
         56 |          3        0.03       80.03
         57 |          1        0.01       80.04
         60 |          1        0.01       80.05
         61 |          2        0.02       80.07
         63 |          1        0.01       80.08
         64 |          1        0.01       80.09
         65 |          1        0.01       80.10
         67 |          2        0.02       80.12
         68 |          2        0.02       80.14
         70 |          1        0.01       80.15
         73 |          1        0.01       80.16
         74 |          2        0.02       80.18
         99 |      1,982       19.82      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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