This paper shows that temporal aggregation affects estimates of trend-cycle variances and of persistence of shocks to economic variables. The authors analyze UCARIMA models with orthogonal components and show two results. First, they prove that when the decay rates of the autocovariance...

In this paper we argue that modelling the trend component in real GNP as a random walk is inconsistent with its interpretation as productivity growth. As an alternative we specify the trend as an Auto Regressive Integrated Moving Average (ARIMA) process, whose impulse response function follows...