IT IS PERHAPS A TRUISM that without lags either in the adjustment of prices and wages or in the transmission of information about prices and wages there would be no business cycle, but rather employment and output would follow presumably smooth paths determined by demographic factors, capital accumulation, and other long-run processes. The observation that movements in wages and prices are correlated with output and employment, and the hypothesis that this phenomenon may be accounted for by adjustment lags in prices and wages are not new and certainly predate both the Phillips [25] paper in 1958 and the Keynesian revolution in macroeconomics. For example, Irving Fisher [5, 6] presented both empirical and theoretical analyses along these lines more than a decade before publication of Keynes' General Theory [15] in 1936. Milton Friedman's [8] analysis of the Phillips curve phenomenon parallels Fisher's thinking quite closely, both emphasizing an hypothesized lag in factor prices behind final product prices attributed at least partially to the existence