Frequencies for first 10,000 rows of shipnum variable in natl1977 dataset :

   Shipment |
     number |      Freq.     Percent        Cum.
------------+-----------------------------------
         01 |      3,149       31.49       31.49
         02 |      4,473       44.73       76.22
         03 |      2,378       23.78      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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