Table 1.
Requirement | Description |
---|---|
Exclusion restriction | Any effect of the instrument on health must be mediated by exposure to the policy of interest |
Exogenous | The instrument must be randomly distributed and uncorrelated with the unobserved or unmeasured characteristics of individuals |
Meaningful effect | The instrument must reliably predict the policy exposure (a strong instrument) |
Monotonic | The effect of the instrument on the policy exposure is not smaller than the exposure that would occur without the instrument |
Stable unit treatment value | The value of the policy variable and the relationship between the policy variable and health outcome in one individual must not be affected by variations in these factors among other individuals |