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Revisiting the Many Instruments Problem using Random Matrix Theory

Helmut Farbmacher, Rebecca Groh, Michael Mühlegger, Gabriel Vollert

arXiv 16 Aug 2024 · Econometrics

arXiv:2408.08580 · PDF · DOI · OpenAlex · Extracted main text

Abstract

Instrumental variables estimation with many instruments is biased. Traditional bias-adjustments are closely connected to the Silverstein equation. Based on the theory of random matrices, we show that Ridge estimation of the first-stage parameters reduces the implicit price of bias-adjustments. This leads to a trade-off, allowing for less costly estimation of the causal effect, which comes along with improved asymptotic properties. Our theoretical results nest existing ones on bias approximation and adjustment with ordinary least-squares in the first-stage regression and, moreover, generalize them to settings with more instruments than observations. Finally, we derive the optimal tuning parameter of Ridge regressions in simultaneous equations models, which comprises the well-known result for single equation models as a special case with uncorrelated error terms.

Citation extraction

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Most heavily cited references

The works this paper leans on most, across its whole bibliography — not restricted to papers in our corpus. Ranked by composite intensity, which combines how often a work is mentioned, how many sections mention it, and how much of that falls in the main text rather than the appendix.

ReferenceIntensityMentionsSectionsMain text
1Hahn, J. and J. Hausman (2002) Notes on bias in estimators for simultaneous equation models1.00053100%
2Dobriban, E. and S. Wager (2018) High-dimensional asymptotics of prediction: Ridge regression and classification0.9285480%
3Chao, J. C. and N. R. Swanson (2005) Consistent estimation with a large number of weak instruments0.87452100%
4Chamberlain, G. and G. Imbens (2004) Random effects estimators with many instrumental variables0.73732100%
5Hahn, J. and J. Hausman (2002) A new specification test for the validity of instrumental variables0.73732100%
6Hansen, C. and D. Kozbur (2014) Instrumental variables estimation with many weak instruments using regularized JIVE0.73732100%
7Nagar, A. L (1959) The bias and moment matrix of the general k-class estimators of the parameters in simultaneous equations0.73732100%
8Donald, S. G. and W. K. Newey (2001) Choosing the number of instruments0.64422100%
9Hastie, T., A. Montanari, S. Rosset, and R. J. Tibshirani (2022) Surprises in high-dimensional ridgeless least squares interpolation0.64422100%
10Dobriban, E. and S. Wager (2018) High-dimensional asymptotics of prediction: Ridge regression and classification0.5854425%

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Cited by, within the corpus

arXiv econ.EM papers that cite this one, ranked by how heavily they lean on it.

Citing paperIntensityMentionsSections
1Robust Inference with High-Dimensional Instruments0.40511