Relevant for measuring the impacts of changes in regimes/shocks. It uses observational study data of the same units across time and requires that the units (firms, individuals or countries) are divided into treatment and control groups. Difference-in-difference estimates the effect of an intervention by comparing the average change in the outcome variable experienced by the treated group over time to the average change in the outcome variable experienced by the control group.

Stated preference – survey method which is typically used to identify a person’s willingness to pay. Its key advantage is that it enables a monetary value to be placed on certain impacts of a policy or measure.