Frequencies for first 10,000 rows of vacuum variable in natl1996 dataset :

     Vacuum |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        543        5.43        5.43
          2 |      9,444       94.44       99.87
          9 |         13        0.13      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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