Frequencies for first 10,000 rows of agi_class variable in zipcode2005 dataset :

  agi_class |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      1,667       16.67       16.67
          2 |      1,667       16.67       33.34
          3 |      1,667       16.67       50.01
          4 |      1,667       16.67       66.68
          5 |      1,666       16.66       83.34
          6 |      1,666       16.66      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 20 Jun 2017