Natural Experiments

“work best in circumstances where a relatively large population is affected by a substantial change in a well-understood environmental exposure, and where exposures and outcomes can be captured through routine data sources, such as environmental monitoring and mortality records”

MRC (2006) Developing and evaluating complex interventions: new guidance
https://webarchive.nationalarchives.gov.uk/ukgwa/20220207162925/http://mrc.ukri.org/documents/pdf/complex-interventions-guidance/