“USA Today has come out with a new survey – apparently, three out of every four people make up 75% of the population.” 
- David Letterman
Effective health planning, policy, and research require an appreciation of who is most at risk, affected, or in need. This means figuring out what we know about a particular group of people – a population – as well as what we don’t know.
Paying attention to the populations under consideration is important because issues play out differently in different places, at different times and among different people. For example, women face greater risks and health effects of exposure to methyl mercury, an environmental contaminant, as compared with men. But all women are not equally at risk of exposure. Women living in First Nations and coastal communities are more likely than many other groups of women to be exposed to methyl mercury because they consume fish, shellfish and marine mammals, which tend to have higher concentrations of the toxin. Furthermore, women who are pregnant or breastfeeding face specific health concerns because methyl mercury can be passed from them to their child.
So when thinking about a population, it is important to ask ourselves:
- Who is most at risk, in need, and/or affected by an issue?
- Have we considered the diverse experiences within a population?
- Who is missing from the evidence or analysis?
By the end of this module you should be able to:
- Describe how a population(s) is defined
- Characterize a population using the core concepts of sex, gender, diversity and equity
- Analyze the impact of population definitions
 Image source: http://flickr.com/photos/proimos/5895689407/