This paper provides weak-instrument asymptotic representations of tests for instrument validity by Hahn and Hausman (HH) [Hahn, J., Hausman, J., 2002. A new specification test for the validity of instrumental variables. Econometrica, Vol. 70, pp. 163-189], and uses these representations to...

This paper extends Staiger and Stock’s (1997) weak instrument asymptotic approximations to the case of many weak instruments by modeling the number of instruments as increasing slowly with the number of observations. It is shown that the resulting “many weak instrument” approximations can...

Weak instruments can produce biased IV estimators and hypothesis tests with large size distortions. But what, precisely, are weak instruments, and how does one detect them in practice? This paper proposes quantitative definitions of weak instruments based on the maximum IV estimator bias, or the...

Weak instruments can produce biased IV estimators and hypothesis tests with large size distortions. But what, precisely, are weak instruments, and how does one detect them in practice? This paper proposes quantitative definitions of weak instruments based on the maximum IV estimator bias, or the...

We review and assess the monetary policy framework currently used by the Federal Reserve, with special focus on policies that operate through the slope of the term structure, including forward guidance and large scale asset purchases. These slope policies are important at the zero lower bound....