Frequencies for first 10,000 rows of hincomer variable in namcs2008 dataset :

  median household income in |
               patient's zip |      Freq.     Percent        Cum.
-----------------------------+-----------------------------------
                missing data |        478        4.78        4.78
quartile 1 ($32,793 or less) |      1,613       16.13       20.91
quartile 2 ($32,794-$40,626) |      2,466       24.66       45.57
quartile 3 ($40,627-$52,387) |      2,649       26.49       72.06
quartile 4 ($52,388 or more) |      2,794       27.94      100.00
-----------------------------+-----------------------------------
                       Total |     10,000      100.00

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