Introductory pages to "Business Cycles, Inflation, and Forecasting, 2nd edition"

Geoffrey H. Moore, Business Cycles, Inflation, and Forecasting, 2nd edition (Ballinger, 1983), https://www.nber.org/books-and-chapters/business-cycles-inflation-and-forecasting-2nd-edition/introductory-pages-business-cycles-inflation-and-forecasting-2nd-edition.