Frequencies for first 10,000 rows of vacuum variable in natlterr1996 dataset :

     Vacuum |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |         40        0.40        0.40
          2 |      9,959       99.59       99.99
          9 |          1        0.01      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 22 Dec 2015