The contemporaneous correlation between price shocks and output shocks
Until the 1990s, prices were believed to be procyclical. Several researchers have since presented evidence of counter-cyclical prices. This evidence proved robust, but its interpretation has varied. Some have argued that the contemporaneous correlation between output and prices reflects both the source of the current shock and the adjustment process from short-run to long-run equilibrium; the adjustment to the long run imparts a bias towards a negative price–output correlation. The issue of dynamics is addressed by estimating price shocks and output shocks. The sign of the correlation between these shocks does not reveal anything about the relative importance or frequency of demand versus supply shocks; however, some understanding is gained from the time-series of the product of the shocks. In periods when the product is negative, supply shocks must have been either relatively large or relatively important. In periods when the product is positive, demand shocks must have been either relatively large or relatively important. The data suggest that the economies of the USA, Canada and the UK were buffeted by both demand and supply shocks in about equal portions.