Frequencies for first 10,000 rows of blodlead variable in nhamcsopd1998 dataset :

 blood lead |
      level |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,885       98.85       98.85
          1 |        115        1.15      100.00
------------+-----------------------------------
      Total |     10,000      100.00

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