Frequencies for first 10,000 rows of vacuum variable in natl1991 dataset :

     Vacuum |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        461        4.61        4.61
          2 |      9,523       95.23       99.84
          9 |         16        0.16      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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