Efficient Policy Learning from Surrogate-Loss Classification Reductions
- URL: http://arxiv.org/abs/2002.05153v1
- Date: Wed, 12 Feb 2020 18:54:41 GMT
- Title: Efficient Policy Learning from Surrogate-Loss Classification Reductions
- Authors: Andrew Bennett and Nathan Kallus
- Abstract summary: We consider the estimation problem given by a weighted surrogate-loss classification reduction of policy learning.
We show that, under a correct specification assumption, the weighted classification formulation need not be efficient for policy parameters.
We propose an estimation approach based on generalized method of moments, which is efficient for the policy parameters.
- Score: 65.91730154730905
- License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
- Abstract: Recent work on policy learning from observational data has highlighted the
importance of efficient policy evaluation and has proposed reductions to
weighted (cost-sensitive) classification. But, efficient policy evaluation need
not yield efficient estimation of policy parameters. We consider the estimation
problem given by a weighted surrogate-loss classification reduction of policy
learning with any score function, either direct, inverse-propensity weighted,
or doubly robust. We show that, under a correct specification assumption, the
weighted classification formulation need not be efficient for policy
parameters. We draw a contrast to actual (possibly weighted) binary
classification, where correct specification implies a parametric model, while
for policy learning it only implies a semiparametric model. In light of this,
we instead propose an estimation approach based on generalized method of
moments, which is efficient for the policy parameters. We propose a particular
method based on recent developments on solving moment problems using neural
networks and demonstrate the efficiency and regret benefits of this method
empirically.
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