An examination of whether one should seasonally adjust data before developing multivariate time series models to provide forecasts.

Three distinct strands can be identified in the literature on seasonality. Economists have long been interested in removing high-frequency "noise" from individual economic time series, or "deseasonalizing the data" in common parlance. The second strand, on which an extensive technical literature...

Separating cyclical movement from trend growth at seasonal and business cycle frequencies is important to macroeconomic research. At business cycle frequencies, time trends, first differences and the more recent Hodrick-Prescott (HP) filter are used to separate trends from cycles. At seasonal...

Empirical tests of the production-smoothing hypothesis have yielded mixed results. In this paper, Donald Allen looks for, and finds evidence of, seasonal production smoothing in 15 out of 25 manufacturing series and 8 out of 10 retail series, using detrended seasonally unadjusted data. The...

A reevaluation of the evidence of seasonality in prices, finding that seasonal price movements have become more prominent in the relatively stable inflation environment that has prevailed since 1982, and that the amount of seasonality differs greatly by item, making it difficult to generalize...

Optimal linear regulator methods are used to represent a class of models of endogenous equilibrium seasonality that has so far received little attention. Seasonal structure is built into these models in either of two equivalent ways: periodically varying the coefficient matrices of a formerly...

In a world where time series show clear seasonal fluctuations, rational agents will take account of those fluctuations in planning their own behavior. Using seasonally adjusted data to model behavior of such agents throws away information and introduces possibly severe bias. Nonetheless it may...