  Many economic studies use shift-share instruments to estimate causal effects.
Often, all shares need to fulfil an exclusion restriction, making the
identifying assumption strict. This paper proposes to use methods that relax
the exclusion restriction by selecting invalid shares. I apply the methods in
two empirical examples: the effect of immigration on wages and of Chinese
import exposure on employment. In the first application, the coefficient
becomes lower and often changes sign, but this is reconcilable with arguments
made in the literature. In the second application, the findings are mostly
robust to the use of the new methods.
