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Hansen, Barrett

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Hansen, Barrett

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Author's Publications: search.filters.isAuthorOfPublication.d0a47b05-2967-4c07-a4f5-04733d0b7ee9

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    Assessing the Effectiveness of Scrubber Installation on Air Pollution Emissions Reductions Among Coal-Fired Power Plants: Application of Statistical Methods for Causal Inference
    (2015-04-08) Hansen, Barrett
    The 1990 amendment to the Clean Air Act implemented a cap-and-trade system that required electricity-generating power plants to dramatically reduce Sulfur Dioxide (SO2) and Nitrogen Oxide (NOx) emissions. Plants impacted by this legislation had a variety of compliance options, including decreasing factory operation, purchasing carbon credits, installing scrubbers, and changing fuel inputs. Using data from 1997-2012 of 995 coal-burning power plants, we examine the effectiveness of scrubber installation in reducing SO2 and NOx emissions. Specifically, we employ two methods—a propensity score algorithm and a matching algorithm—to estimate: 1) the causal effect of scrubber installation prior 1997 on the emissions during 1997; and 2) the causal effect of scrubber installation at any time during the period 1997-2012 on emissions two months following scrubber installation. Using a propensity score method, we found that pre-1997 SO2 scrubbers reduced 1997 SO2 emissions by 68% (95% CI 58% to 76%), and pre-1997 NOx scrubbers reduced 1997 NOx emissions by 28% (16%, 38%). Additionally, installing SO2 and NOx scrubbers at any time during the period 1997-2012 reduces SO2 and NOx emissions by 89% (88%, 90%) and 21% (19%, 24%) two months following installation, respectively. These final two results are corroborated by a matching algorithm, which finds scrubbers cause SO2 and NOx emissions decline by 88% (87%, 89%) and by 20%. (17%, 22%) two months following installation, respectively.
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    Primary Elections and Partisan Polarization in the U.S. Congress
    (Now Publishers, 2010) Hirano, Shigeo; Snyder, James; Ansolabehere, Stephen; Hansen, Barrett
    Many observers and scholars argue that primary elections contribute to ideological polarization in U.S. politics. We test this claim using congressional elections and roll call voting behavior. Many of our findings are null. We find little evidence that the introduction of primary elections, the level of primary election turnout, or the threat of primary competition are associated with partisan polarization in congressional roll call voting. We also find little evidence that extreme roll call voting records are positively associated with primary election outcomes. A positive finding is that general election competition exerts pressure toward convergence as extreme roll call voting is negatively correlated with general election outcomes.