Frequencies for first 10,000 rows of vacuum variable in natl2000 dataset :

     Vacuum |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        491        4.91        4.91
          2 |      9,469       94.69       99.60
          9 |         40        0.40      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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