Frequencies for first 10,000 rows of blodlead variable in nhamcsopd2000 dataset :

 blood lead |
      level |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,933       99.33       99.33
          1 |         67        0.67      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 28 Mar 2016