I wonder if economics has less basic core material than is necessary for fields such as mathematics, physics, or chemistry, say.

A teacher told my mother that I would never become successful, which illustrates the difficulty of long-run forecasting on inadequate data.

Rob Engle and I are concerned with extracting useful implications from economic data, and so the properties of the data are of particular importance.

A potentially useful property of forecasts based on cointegration is that when extended some way ahead, the forecasts of the two series will form a constant ratio, as is expected by some asymptotic economic theory.