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>> Meet Joe. He’s an analyst, and today we are going to help him find the data that he needs to describe how the health of Canadians varies by income.
Joe has recently read CIHI’s Trends in Income-Related Health Inequalities report…
…and learned that for many indicators, the gaps in health between Canadians with the highest and lowest income levels are large and have generally not narrowed over the past decade.
In some cases, gaps in health have widened over time.
Consider the following scenario. Let’s say that the rate of hospitalization in the lowest income level is 10 for every 100 people and the rate in the highest income level is 5 for every 100 people.
The rate for the lowest income level is 2 times higher than the rate for the highest. This is the RELATIVE inequality.
The rate for the lowest income level is also higher by 5 more cases for every 100 people. This is the ABSOLUTE inequality.
Now, for illustrative purposes let’s keep the gap in the observed rates the same but shift all rates up by 15 so that the rate for the lowest income level is now 25 for every 100 people and for the highest income level, 20 for every 100 people. Now we have shifted the rates higher.
Let’s calculate again the size of the inequality by starting with the rate ratio.
The rate for the lowest income level is now 1.25 times higher than the rate for the highest level. This relative inequality is much smaller than it was when all of the rates were lower in Scenario 1. By shifting the rates higher but keeping the gap the same, the relative inequality has decreased.
The rate for the lowest income level is still higher by 5 more cases for every 100 people. This absolute inequality is the same as in Scenario 1, even though the relative inequality has decreased.
What does this mean?
If the gap were eliminated in both scenarios, hospitalizations would be reduced by the same number: 5 fewer cases per 100 people.
This is despite the fact that the relative inequality is lower for Scenario 2.
OK, Joe gets it. When the overall rates are lower, a small absolute difference may still result in a high level of relative inequality.
When the overall indicator rates are higher, however, large relative inequality occurs only when there is also a large difference between the 2 income levels being compared.
Joe now understands that the inequality measures are influenced by the underlying indicator rate and that the conclusions drawn from inequality results based on the absolute and relative scales are not always the same. It is helpful to review both types of inequality measures as he examines the data.
Higher inequalities on either scale may signal a need to focus attention on reducing inequalities.
After exploring the Health Inequalities Interactive Tool further, Joe is now ready to write his briefing note.
“Inequalities are large for smoking and COPD hospitalization and have widened over the past decade.”
“Although B.C. has low overall rates of COPD hospitalization, the rates are still approximately 4 times higher among those in the lowest income level.”
By basing his analysis on both relative and absolute inequality data, Joe will ensure that his director has the tools she needs to make a more informed decision.
If you’d like to learn more about the Trends in Income-Related Health Inequalities project, please visit CIHI’s website at www.cihi.ca.
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