Frequencies for first 10,000 rows of blodlead variable in nhamcsopd1997 dataset :

 blood lead |
      level |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,876       98.76       98.76
          1 |        124        1.24      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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