Frequencies for first 10,000 rows of shipnum variable in natl1972 dataset :

   Shipment |
     number |      Freq.     Percent        Cum.
------------+-----------------------------------
         01 |      2,083       20.83       20.83
         02 |      2,481       24.81       45.64
         03 |      2,484       24.84       70.48
         04 |      2,354       23.54       94.02
         05 |        578        5.78       99.80
         99 |         20        0.20      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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