Data mining and the selection of instruments

Instrumental variables estimation is widely applied in econometrics. To implement the method, it is necessary to specify a vector of instruments. In this paper, it is argued that there are compelling reasons to use the data for instrument selection, but that it is desirable to ensure the resulting estimator still behaves in the way predicted by standard textbook theory. These arguments lead one to propose three criteria for data based instrument selection. The remainder of the paper assesses the extent to which these criteria are met by two algorithms for data based instrument selection. The first algorithm is the method of structurally ordered instrumental variables proposed in the context of economy-wide linear simultaneous equation models. The second algorithm is proposed in the context of the method of generalized instrumental variables, which is commonly used to estimate the parameters of Euler equation models.