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Bayesian A/B inference (BABI) is a method that combines subjective prior information with data from A/B experiments to provide inference for lift – the difference in a measure of response in control and treatment, expressed as its ratio to the measure of response in control. The procedure is embedded in stable code that can be executed in a few seconds for an experiment, regardless of sample size, and caters to the objectives and technical background of the owners of experiments. BABI provides more powerful tests of the hypothesis of the impact of treatment on lift, and sharper conclusions about the value of lift, than do legacy conventional methods. In application to 21 large online experiments, the credible interval is 60% to 65% shorter than the conventional confidence interval in the median case, and by close to 100% in a significant proportion of cases; in rare cases, BABI credible intervals are longer than conventional confidence intervals and then by no more than about 10%.

The paper published below was prepared by Taylor Ostrander for Frank Knight’s course, Economic Theory, Economics 301, during the Fall 1933 quarter.

The Bureau of Economics in the Federal Trade Commission has a three-part role in the Agency and the strength of its functions changed over time depending on the preferences and ideology of the FTC’s leaders, developments in the field of economics, and the tenor of the times. The over-riding current role is to provide well considered, unbiased economic advice regarding antitrust and consumer protection law enforcement cases to the legal staff and the Commission. The second role, which long ago was primary, is to provide reports on investigations of various industries to the public and public officials. This role was more recently called research or “policy R&D”. A third role is to advocate for competition and markets both domestically and internationally. As a practical matter, the provision of economic advice to the FTC and to the legal staff has required that the economists wear “two hats,” helping the legal staff investigate cases and provide evidence to support law enforcement cases while also providing advice to the legal bureaus and to the Commission on which cases to pursue (thus providing “a second set of eyes” to evaluate cases). There is sometimes a tension in those functions because building a case is not the same as evaluating a case. Economists and the Bureau of Economics have provided such services to the FTC for over 100 years proving that a sub-organization can survive while playing roles that sometimes conflict. Such a life is not, however, always easy or fun.

This paper proposes a new theoretical framework to explain enterprise unionism and conducts the first systematic comparative study of union structure in nine Asian countries. Our framework emphasizes political dynamics and the role of the state in labor relations and argues that the initial period of the collective bargaining era constituted a critical juncture (state labor policy) that occurred in distinctive ways in different countries and that these differences played a central role in shaping the different union structures in the following decades. The nine countries are mainly divided into three groups, depending on the type of state labor policy: enforcement of enterprise unionism; centralization/laissez-faire (non-enterprise unionism); and dual unionism/gradual transition (middle-ground). Governmental data were used for the study. A clear correspondence between state labor policy and union structure in each of these groups was found. We believe that our framework significantly enhances our understanding of the Asian cases. Future research should explore the validity of the proposed framework through comparative studies of Latin American cases where enterprise unions have also been observed.

Plus Factors have long played an important role in inferring a price agreement from the totality of the evidence. In response to changes in the case law, economists have proposed two alternative paths for the future of price fixing analysis. This paper evaluates the suggested approaches and recommends retaining the enhanced Plus Factor methodology.

By carefully defining the Plus Factor concept, three key components of the analysis emerge: (1) information on communications associated with the alleged agreement, (2) economic considerations affecting market competition, and (3) characteristics that serve to differentiate explicit from tacit collusion.

Developments rationalizing the Plus Factor concept show promise, as the methodology is not more closely related to economic theory. On the other hand, replacement of the Plus Factor methodology with one focused on market performance seems problematic. By abandoning the Plus Factor concept, the economist loses a key institutional constraint on over-aggressive enforcement.

Until advocates can address the difficulties associated with using performance evidence to identify price fixing, the standard Plus Factor concept appears more appropriate. Thus, antitrust analysts should continue to use the Plus Factor methodology to infer agreements in price fixing investigations, as long as the economic rationalization of the specific Plus Factor is clearly presented.

The paper synthesizes a number of recent contributions to the price fixing literature and addresses key issues of interest to the enforcement community. By providing a critique of the proposed policy shift to use performance evidence to infer price fixing liability, the study serves to justify continued application of the Plus Factor methodology.