Frequencies for first 10,000 rows of drugtest variable in person dataset :

  DRUG TEST |
       TYPE |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      7,101       71.01       71.01
          1 |      1,604       16.04       87.05
          2 |        141        1.41       88.46
          7 |          1        0.01       88.47
          8 |         29        0.29       88.76
          9 |      1,124       11.24      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 18 Apr 2016