In this paper we put forward a new time series model, which describes nonlinearity and seasonality simultaneously. We …-transition nonlinearity and for time-varying seasonality. We find that the model fits the data well for 14 of the 18 series. We also consider … out-of-sample forecasting where we compare forecasts from the SEASTAR models with forecasts from nested models. It turns …

-run equilibrium) for the retailers' side. The explicit modeling of nonlinearities does not improve out-of-sample forecasting …