
The
Public Health Disparities Geocoding Project Monograph 

Geocoding
and Monitoring US Socioeconomic Inequalities in Health: An introduction to using areabased socioeconomic measures 
WHY? 
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STEP
BY STEP COMPARISON 

Step
7: Estimate the relative index of inequality (RII) for CT level poverty in relation to all cause mortality. 

SAS
PROGRAMMING click here to download SAS program 

a. Estimate the approximate cumulative distribution function for CT poverty, based on the population denominator for each poverty stratum (summed up over age). b. Calculate the expected cases in each CT poverty stratum, based on the agestandardized incidence rate. c. Fit a Poisson log linear model, modeling the expected number of cases as a function of the approximate cumulative distribution of CT poverty, using the population denominator as an offset. d. Exponentiate the beta term from this model to get the relative index of inequality. 
5.
Relative Index of Inequality (RII) In practice,
this latter quantity is represented by the cumulative distribution function
(cdf). We approximate the cdf for the jth level of a given ABSM by summing
the proportion of the population represented by the categories ABSM

data
Step7a Step7b ; set Step5c END=LASTOBS; by CINDPOV ; retain dxden ;
if _N_=1 then do ;
DUMMY=1 ; data Step7c ;
CRCNT=CRDEN*IRW
; ods output ParameterEstimates=param
; data Step7d;

. 

We
determine the “marginal” cumulative distribution function, cdf(ABSMj ),
of the ABSM over the entire population, as noted above. 

To calculate the agestandardized RIIst, we fit the following Poisson model for the expected cases:  
Exponentiation of the ß1 yields the RII, which is interpretable as an incidence rate ratio comparing the rates in the bottom to the top of the socioeconomic hierarchy. A larger RII indicates a greater the degree of inequality across a socioeconomic hierarchy, which may be due to a steep socioeconomic gradient or large inequalities in the distribution of the ABSM itself. 
This
work was funded by the National Institutes of Health (1RO1HD3686501)
via the National Institute of Child Health & Human Development (NICHD)
and the Office of Behavioral & Social Science Research (OBSSR). 

Copyright
© 2004 by the President and Fellows of Harvard College  The Public
Health Disparities Geocoding Project. 