Giorgio Canarella and Stephen M. Miller (Economics) published their paper "Does U.K.’s Real GDP Have a Unit Root? Evidence from a Multi-Century Perspective" in Applied Economics with co-authors Rangan Gupta, University of Pretoria, and Tolga Omay, Atilim University. A recent nonlinear unit-root test as well as other linear and nonlinear tests examine the stationarity of five multi-century historical United Kingdom series of real output compiled by the Bank of England. Three series span 1270 to 2016 and two series span 1700 to 2016. These datasets represent the longest span of historical real output data available and, thus, provide the environment for which unit-root tests are most powerful. A key feature of the new nonlinear test is its simultaneous allowance for two types of nonlinearity: time-dependent (structural breaks) nonlinearity and state-dependent (asymmetric adjustment) nonlinearity. The key finding of the test, contrary to more popular nonlinear unit-root test, provides strong evidence that the main structure of the five series is a stationary process characterized by an asymmetric nonlinear adjustment and a permanent break affecting both the intercept and the trend. Thus, fiscal and/or monetary stabilization policies have only temporary effects on the output levels of the U.K.
