Frequencies for first 10,000 rows of dfage variable in natl1988 dataset :

     Age of |
     Father |      Freq.     Percent        Cum.
------------+-----------------------------------
         15 |          1        0.01        0.01
         16 |          7        0.07        0.08
         17 |         31        0.31        0.39
         18 |         86        0.86        1.25
         19 |        150        1.50        2.75
         20 |        220        2.20        4.95
         21 |        257        2.57        7.52
         22 |        327        3.27       10.79
         23 |        388        3.88       14.67
         24 |        414        4.14       18.81
         25 |        509        5.09       23.90
         26 |        474        4.74       28.64
         27 |        504        5.04       33.68
         28 |        478        4.78       38.46
         29 |        500        5.00       43.46
         30 |        408        4.08       47.54
         31 |        390        3.90       51.44
         32 |        341        3.41       54.85
         33 |        292        2.92       57.77
         34 |        237        2.37       60.14
         35 |        237        2.37       62.51
         36 |        174        1.74       64.25
         37 |        172        1.72       65.97
         38 |        110        1.10       67.07
         39 |         94        0.94       68.01
         40 |         90        0.90       68.91
         41 |         54        0.54       69.45
         42 |         38        0.38       69.83
         43 |         41        0.41       70.24
         44 |         37        0.37       70.61
         45 |         19        0.19       70.80
         46 |         10        0.10       70.90
         47 |         12        0.12       71.02
         48 |         11        0.11       71.13
         49 |          8        0.08       71.21
         50 |          7        0.07       71.28
         51 |          5        0.05       71.33
         52 |          6        0.06       71.39
         53 |          3        0.03       71.42
         54 |          2        0.02       71.44
         55 |          3        0.03       71.47
         56 |          2        0.02       71.49
         58 |          1        0.01       71.50
         61 |          1        0.01       71.51
         62 |          1        0.01       71.52
         65 |          1        0.01       71.53
         99 |      2,847       28.47      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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