Frequencies for first 10,000 rows of pctpovr variable in nhamcsopd2006 dataset :

 percent pop below poverty level in |
                 patient's zip code |      Freq.     Percent        Cum.
------------------------------------+-----------------------------------
Quartile 1 (Less than 5.00 percent) |      1,476       14.76       14.76
     Quartile 2 (5.00-9.99 percent) |      2,433       24.33       39.09
   Quartile 3 (10.00-19.99 percent) |      3,334       33.34       72.43
 Quartile 4 (20.00 percent or more) |      2,188       21.88       94.31
                       Missing data |        569        5.69      100.00
------------------------------------+-----------------------------------
                              Total |     10,000      100.00

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