1. In the first part, please describe the main issue and the method at hand including a critical assessment of the method, 5 pages, 5 sources. 
2. In the second part, present an application of the method in any economics-related topic including a literature reviiew, 10 pages, 20 sources.

Once there is endogeneity, e.g. reverse causality, one can use the variation of a variable that is correlated with the endogenous variable, but not affected by the dependent variable.