Frequencies for first 10,000 rows of vacuum variable in natl1999 dataset :

     Vacuum |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        540        5.40        5.40
          2 |      9,434       94.34       99.74
          9 |         26        0.26      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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