Frequencies for first 10,000 rows of year variable in cowbo19ages dataset :

       Year |      Freq.     Percent        Cum.
------------+-----------------------------------
       1969 |      4,392       43.92       43.92
       1970 |      4,485       44.85       88.77
       1971 |      1,123       11.23      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 2 May 2017