Assessing the impact of natural policy experiments on socioeconomic inequalities in health: how to apply commonly used quantitative analytical methods?

Table 4 Observed and predicted prevalence of poor health, rate difference and rate ratio for low and high educated groups with and without the implementation of the policy, as obtained using the seven methods

	Low-educated (%)	High-educated (%)	Rate difference	Rate ratio
Observed prevalence with policy effect	16.63	7.49	9.14	2.22
Predicted prevalence without the policy effect^a
Regression adjustment	19.11	8.00	11.11	2.39
Propensity score matching	19.03	7.99	11.04	2.38
Difference-in-differences analysis	18.97	7.98	10.99	2.38
Fixed effects models	18.84	7.88	10.96	2.39
Instrumental variable analysis	19.15	7.99	11.16	2.40
Regression discontinuity	Not comparable	Not comparable	Not comparable	Not comparable
Interrupted time-series	18.96	7.97	10.99	2.38

^aAs derived from the stratified analyses, reported as proportion of individuals with poor health (or, equivalently, individual probability of having poor health)

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