[ares2012]

Business cycles are often a component of what is a composite function of the time series. So the time series itself might not have perfect cycles but the business cycle is usually one of the principal components of the time series, which is what I think they were referring to.

For example, the price of commodities does depend on the growing season (which is predictable) but other factors which are not cyclical so that the price itself is not easily predicted.