Other approaches for the estimation of causal effects with some invalid IVs have been proposed. Kang et al. have proposed a method based on penalized regression for detecting and accounting for invalid instruments that provides a consistent estimate of causal effect if at least 50% of the genetic variants are valid (Kang et al., 2015). Han has proposed a similar penalized estimator within the generalized method of moments framework, again with a 50% breakdown level (Han, 2008). Kolesár et al. have proposed a method within the framework of k‐class estimators with a 100% breakdown level under the InSIDE assumption (Kolesár et al., 2014). The first two methods are similar to the median‐based approaches proposed here, and the final method is similar to MR‐Egger regression. An alternative approach was proposed by Windmeijer et al. based on Hansen's overidentification test, a test of the homogeneity of the ratio estimates from different candidate IVs (Windmeijer et al., 2015). The basic idea of this approach is to report a causal estimate based on genetic variants whose ratio estimates are mutually similar. A related approach
