econometrics Article Do Seasonal Adjustments Induce Noncausal Dynamics in Inflation Rates? Alain Hecq 1, Sean Telg 1,* and Lenard Lieb 2 1 Department of Quantitative Economics, Maastricht University, School of Business and Economics, P.O. Box 616, 6200 MD Maastricht, The Netherlands;
[email protected] 2 Department of General Economics (Macro), Maastricht University, School of Business and Economics, P.O. Box 616, 6200 MD Maastricht, The Netherlands;
[email protected] * Correspondence:
[email protected]; Tel.: +31-43-38-83578 Academic Editors: Gilles Dufrénot, Fredj Jawadi, Alexander Mihailov and Marc S. Paolella Received: 12 June 2017; Accepted: 17 October 2017; Published: 31 October 2017 Abstract: This paper investigates the effect of seasonal adjustment filters on the identification of mixed causal-noncausal autoregressive models. By means of Monte Carlo simulations, we find that standard seasonal filters induce spurious autoregressive dynamics on white noise series, a phenomenon already documented in the literature. Using a symmetric argument, we show that those filters also generate a spurious noncausal component in the seasonally adjusted series, but preserve (although amplify) the existence of causal and noncausal relationships. This result has has important implications for modelling economic time series driven by expectation relationships. We consider inflation data on the G7 countries to illustrate these results. Keywords: inflation; seasonal adjustment filters; mixed causal-noncausal models JEL Classification: C22; E37 1. Introduction Most empirical macroeconomic studies are based on seasonally adjusted data. Various methods have been proposed in the literature aiming at removing unobserved seasonal patterns without affecting other properties of the time series. Just as the misspecification of a trend may cause spurious cycles in detrended data (e.g., Nelson and Kang 1981), a wrongly specified pattern at the seasonal frequency might have very undesirable effects (see, e.g., Ghysels and Perron 1993; Maravall 1993).