Frequencies for first 10,000 rows of vacuum variable in natl1993 dataset :

     Vacuum |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        469        4.69        4.69
          2 |      9,521       95.21       99.90
          9 |         10        0.10      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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