Frequencies for first 10,000 rows of flag77 variable in natl1971 dataset :

    77 & 77 |
Combination |
       Flag |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         21        0.21        0.21
          . |      9,979       99.79      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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