Amy Semet has posted this draft on SSRN.  Here is the abstract:

ow do administrative agencies interpret statutes? Despite the theoretical treatment scholars offer on how agencies construe statutes, far less is known empirically about administrative statutory interpretation even though agencies play a critical role in interpreting statutes. This Article looks behind the black box of agency statutory interpretation to review how administrative agencies use canons and other tools of statutory interpretation to decide cases. Surveying over 7,000 cases heard by the National Labor Relations Board (“NLRB”) from 1993-2016, I analyze the statutory methodologies the Board uses in its decisions in order to uncover patterns of how the Board interprets statutes over time. Overall, I find no ideological coherence to statutory methodology. Board members switch between textualist or purposive methods depending upon the partisan outcome sought. Indeed, Board members often use statutory methodologies to dueling purposes, with majority and dissenting Board members using the same statutory methodology to support contrasting outcomes. The Board has also changed how it interprets statutes over time, relying in recent years more on vague pronouncements of policy and less on precedent or legislative history. Moreover, despite scholars arguing that agencies should interpret statutes differently than courts, in practice, this study indicates that the NLRB interprets its governing statute in similar fashion to how courts do. After analyzing the empirical data, I set forth policy recommendations for how agencies should interpret statutes. The balance required—between policy coherence, stability and democratic accountability—is fundamentally different in the context of agency statutory interpretation than for interpretation by a judicial body. Rather than acting like a court, adjudicative agencies like the NLRB should leverage their expertise to arrive at an interpretation that best effectuates the purpose of the statute. For an agency like the NLRB that makes decisions almost exclusively through adjudication this may necessitate that the agency reveal its statutory interpretation in a more transparent fashion through rulemaking.