Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Combining Observational and Experimental Data Using First-stage
  Covariates   Randomized controlled trials generate experimental variation that can
credibly identify causal effects, but often suffer from limited scale, while
observational datasets are large, but often violate desired identification
assumptions. To improve estimation efficiency, I propose a method that combines
experimental and observational datasets when 1) units from these two datasets
are sampled from the same population and 2) some characteristics of these units
are observed. I show that if these characteristics can partially explain
treatment assignment in the observational data, they can be used to derive
moment restrictions that, in combination with the experimental data, improve
estimation efficiency. I outline three estimators (weighting, shrinkage, or
GMM) for implementing this strategy, and show that my methods can reduce
variance by up to 50% in typical experimental designs; therefore, only half of
the experimental sample is required to attain the same statistical precision.
If researchers are allowed to design experiments differently, I show that they
can further improve the precision by directly leveraging this correlation
between characteristics and assignment. I apply my method to a search listing
dataset from Expedia that studies the causal effect of search rankings, and
show that the method can substantially improve the precision.

26
The categories of this paper are: bayes-an
25
The categories of this paper are: patt-sol
14
The categories of this paper are: math-ph
22
The categories of this paper are: chao-dyn
37
The categories of this paper are: supr-con
21
The categories of this paper are: adap-org
35
The categories of this paper are: mtrl-th
24
The categories of this paper are: dg-ga
20
The categories of this paper are: acc-phys
32
The categories of this paper are: atom-ph
9
The categories of this paper are: nlin
17
The categories of this paper are: q-fin
3
The categories of this paper are: physics
28
The categories of this paper are: alg-geom
7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas