What Works for Health (WWFH) is an evidence clearinghouse based on a model of population health that emphasizes factors that can make communities healthier places to live. Analysts review research to rate strategies’ effectiveness in improving health and advancing equity. Strategies include policies, programs, and systems and environmental changes. This image outlines the process that analysts follow.

Graphic showing What Works for Health research process

What Works for Health methods process

Gather and screen evidence

Literature Search

Analysts begin with a broad literature search to define what will be included in each strategy and identify appropriate search terms. Next, analysts conduct a focused search, prioritizing systematic reviews and peer-reviewed articles. Finally, analysts search grey literature and other evidence clearinghouses that assess policy and program effectiveness.

Learn more about WWFH literature searches and sources.

Literature Screen

Analysts screen articles by date, relevance, applicability of findings, study type and authors’ possible conflicts of interest. They retain the most relevant, recent, rigorous reviews and articles.

Analyze and rate evidence

Analysts record sources’ key findings and quality. This includes consideration for study design, quality, and strength of finding(s). Analysts then assess the strength of the body of evidence, which includes the number and duration of studies and the consistency of their findings. Analysts then assign initial evidence and disparity ratings. A second analyst reviews a summary of the evidence and assigns an independent rating. Final ratings are assigned based on the assessment of both analysts.

Learn about our rating guidelines.

Evidence Rating

Analysts assign strategies’ evidence ratings based on quality, quantity and findings of relevant research. Studies with designs that demonstrate causality are given the most weight. Ratings are based on the likelihood of achieving specific outcomes, labeled expected benefits. Outcomes with weaker or less evidence are labeled potential benefits.

Evidence RatingMeaning
Evidence Rating Icon - Scientifically Supported
Strategies rated Scientifically Supported are most likely to make a difference. Multiple robust studies show consistently favorable results.
Evidence Rating Icon - Some Evidence
Strategies rated Some Evidence are likely to work, but more research is needed to confirm effects. These strategies have been tested more than once and results trend favorable.
Evidence Rating Icon - Expert Opinion
Strategies rated Expert Opinion are recommended by credible, impartial experts but have limited research documenting effects. More research, often with stronger designs, is needed to confirm effects.
Evidence Rating Icon - Insufficient Evidence
Strategies rated Insufficient Evidence have limited research documenting effects. These strategies need more research, often with stronger designs, to confirm effects.
Evidence Rating Icon - Mixed Evidence
Strategies rated Mixed Evidence have been tested more than once and results are inconsistent. More research is needed to confirm effects. 
Evidence Rating Icon - Evidence of Ineffectiveness
Strategies rated Evidence of Ineffectiveness are not good investments. Multiple studies show consistently unfavorable or harmful results.

Disparity Rating

Analysts assign each strategy a disparity rating based on research about how a strategy may affect disparities (e.g., racial/ethnic, socioeconomic, or geographic disparities) for health and the social determinants of health. Analysts also consider each strategy’s characteristics, such as population, delivery method and cultural considerations. A strategy’s impact on disparities may change depending on how it is implemented (e.g., tailoring a strategy toward a specific population).  

Some strategies also feature an expanded disparity rating to indicate potential impact on disparities and describe the strength of the evidence supporting the rating. The expanded ratings are part of WWFH’s equity analysis.

Expanded Disparity RatingMeaning
Disparity Rating Icon - Potential to Decrease Disparities
Evidence, expert opinion, or intervention design suggests that these strategies have the potential to decrease or eliminate disparities between subgroups. 
Disparity Rating Icon - Potential to Increase Disparities
Evidence, expert opinion, or intervention design suggests that these strategies have the potential to increase or exacerbate disparities between subgroups.
Disparity Rating Icon - Potential for Mixed Disparities Icon
Evidence or expert opinion suggest these strategies could increase and decrease disparities between subgroups.
Disparity Rating Icon - Inconclusive Impact on Disparities
There is not enough evidence to assess a strategy’s potential impact on disparities. 
Disparity RatingMeaning
Likely to decrease disparities Strategies that are likely to reduce differences in health outcomes (i.e., close a gap)
Likely to increase disparitiesStrategies likely to exacerbate differences
No impact on disparities likelyStrategies that generally benefit entire populations
Summarize and review

Analysts draft a summary of the key findings that support the evidence rating and clarify to which subgroups and outcomes it applies. Strategies with an expanded disparity rating also feature a historical context section and equity considerations. Equity considerations can help users gauge whether a strategy fits their community’s needs and can guide conversations during implementation.

Implementation Examples and Resources

Analysts include examples of strategies in action and tools to support implementation. Examples come from the literature review and from additional focused searches.

Let us know if your community has implemented a strategy and would like to share your story. 

Decision Makers and Expert Review

For every strategy, analysts assign decision makers, or those who often lead initiating or implementing a strategy. These are based on the literature review and can change over time.

External experts are invited to review each strategy and identify ratings they deem incorrect or inappropriate based on their knowledge of literature in the field.