Discuss the use of natural experiments in causal inference.

Natural experiments are a cornerstone in causal inference, offering a unique lens through which we can discern the cause-and-effect relationships in scenarios where controlled experiments are either impractical or ethically unfeasible. The essence of natural experiments lies in their ability to leverage exogenous variations—events that are external to the system being studied and therefore not caused by the dependent or independent variables within that system.

Allow me to illustrate this with a concrete example: the introduction of a new legislation aimed at reducing pollution levels in a specific geographic area. This legislative change can be considered an exogenous shock, as it's an external intervention not influenced by the area's pollution levels or any related factors within that locality....