Frequencies for first 10,000 rows of vacuum variable in natl1998 dataset :

     Vacuum |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |        657        6.57        6.57
          2 |      9,313       93.13       99.70
          9 |         30        0.30      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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