Frequencies for first 10,000 rows of shipnum variable in natl1981 dataset :

   Shipment |
     number |      Freq.     Percent        Cum.
------------+-----------------------------------
         03 |      9,915       99.15       99.15
         06 |         25        0.25       99.40
         09 |         34        0.34       99.74
         15 |         26        0.26      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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