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Historical vs. Current, Marginal Effects
When attempting to quantify the impact of direct health-related factors, it is important to make a distinction between how much of our current health is related to these factors versus how much of our current health can be improved by interventions that target particular factors. Grasping this distinction is critical so that we know where our dollars are best spent to maximize health improvement. In other words, how much have each of these factors affected our health in the past through today versus how much could they affect health in the future if policy was immediately changed? For example, a disease like smallpox has a huge direct effect on health outcomes, but it has essentially been eradicated, so an additional investment in eradicating smallpox has virtually no marginal gains, even though the disease is closely linked to health.

It is also relevant to consider the timespan on which we see certain effects taking place, especially when considering policy intervention. For example, with an environmental change such as improving the air quality, it would take a significant amount of time for all measurable changes in health outcomes to manifest; other interventions, such as dramatically increasing flu vaccination rates, could have significant health outcomes that would be observable on a much shorter timescale.

Correlations vs. Causation
Considering the available literature on social determinants of health and the links between these factors and measurable health outcomes, it is critical to clarify whether what we are observing or seeking is a correlation or causation. Correlations can guide hypothesis generation, but only causation is actionable in terms of policy.

Finally, it is worth considering how a framework like this relates to policy intervention. The specific interventions that might be effective within a category (e.g., health behaviors) could change over time. For example, promotion of wearing motor vehicle seat belts was an important area for policy interventions in the 1970s and 1980s, but is less so now because doing so has become commonplace. Though health behaviors remain relevant to health today, the class of interventions that would have the largest impact are different.