Frequencies for first 10,000 rows of vacuum variable in natl1989 dataset :

     Vacuum |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        320        3.20        3.20
          2 |      9,621       96.21       99.41
          9 |         59        0.59      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 3 Jan 2016