Measuring trend output: how useful are the Great Ratios?

Standard macroeconomic models suggest that the 'great ratios' of consumption to output and investment to output should be stationary. The joint behaviour of consumption, investment and output can then be used to measure trend output. We adopt this approach for the USA and UK, and find support for stationarity of the great ratios when structural breaks are taken into account. From the estimated vector error correction models, we extract multivariate estimates of the permanent component in output, and comment on trend growth in the 1980s and the New Economy boom of the 1990s.