The ever present possibility of confounding factors creates difficulties in identifying causal effects on the basis of observational data. A large number of approaches to resolve this difficulty have been proposed; see Zaman (2010) for a recent survey. One involves using a "natural experiment"...

The ever present possibility of confounding factors creates difficulties in identifying causal effects on the basis of observational data. A large number of approaches to resolve this difficulty have been proposed; see Zaman (2010) for a recent survey. One involves using a "natural experiment"...

Causality is important for empirical analysis in economics but not easily detected. Therefore, it is always important that one should investigate the problem not only on statistical grounds but also add extra statistical information which may come from economic events happening over a time about...