Frequencies for first 10,000 rows of hincomer variable in nhamcsed2006 dataset :

  median household income in |
          patient's zip code |      Freq.     Percent        Cum.
-----------------------------+-----------------------------------
  quartile 1 (below $32,793) |      2,642       26.42       26.42
quartile 2 ($32,793-$40.626) |      2,530       25.30       51.72
quartile 3 ($40,626-$52,387) |      2,090       20.90       72.62
quartile 4 ($52,388 or more) |      2,294       22.94       95.56
                missing data |        444        4.44      100.00
-----------------------------+-----------------------------------
                       Total |     10,000      100.00

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