His research is in macroeconomics and econometrics. He is Founding President of the Society for Economic Measurement, Founding Editor of the Cambridge University Press journal, Macroeconomic Dynamics and of the Emerald Group Publishing monograph series, International Symposia in Economic Theory and Econometrics, and originator of the Divisia monetary aggregates and the "Barnett critique". In consumer demand and production modelling, he originated the Laurent series approach to specification design and the seminonparametric approach using the Müntz–Szász theorem. His publications on bifurcation analysis and nonlinear dynamics have shown that robustness of dynamical inferences is compromised, when policy simulations are run only at point estimates of parameters, since confidence regions about those estimates are often crossed by bifurcation boundaries. He is a Fellow of the American Statistical Association, a Charter Fellow of the Journal of Econometrics, a Charter Fellow of the Society for Economic Measurement, a Fellow of the World Innovation Foundation, a Fellow of the IC² Institute, and a Fellow of the Johns Hopkins Institute for Applied Economics, Global Health, and the Study of Business Enterprise, and Honorary Professor at Henan University in Kaifeng, China. He is ranked among the top 2% of the world's economists in RePEc. His book with Nobel Laureate, Paul A. Samuelson, Inside the Economist's Mind: Conversations with Eminent Economists, Wiley-Blackwell Publishing,, has been translated into seven languages. His MIT Press book, Getting It Wrong: How Faulty Monetary Statistics Undermine the Fed, the Financial System, and the Economy,, won the American Publishers Award for Professional and Scholarly Excellence for the best book published in economics during 2012. During January 2017, he was interviewed in depth about his life's work by Apostolos Serletis. A was held at the Bank of England on May 23–24, 2017.
Honorary journal special issues
Special issues of two eminent professional journals, the Journal of Econometrics and Econometric Reviews, have been published in Professor Barnett's honor with contribution by many of the world's most prominent economists. These journals are:
Special issue of the Journal of Econometrics on the topic of "," coedited in honor of William A. Barnett by James Heckman and Apostolos Serletis, v. 183, no. 1, November 2014, pp. 1 – 146.
Special issue of Econometric Reviews on the topic of "," coedited by James Heckman and Apostolos Serletis, v. 34, no. 1-2, 2015, pp. 1 – 254.