This paper shows how monthly data and forecasts can be used in a systematic way to improve the predictive accuracy of a quarterly macroeconometric model. The problem is formulated as a model pooling procedure (equivalent to non-recursive Kalman filtering) where a baseline quarterly model forecast is modified through 'add-factors' or 'constant adjustments'. The procedure 'automatically' constructs these adjustments in a covariance-minimizing fashion to reflect the revised expectation of the quarterly model's forecast errors, conditional on the monthly information set. Results obtained using Federal Reserve Board models indicate the potential for significant reduction in forecast error variance through application of these procedures.
K E Y \\ORUSForecasting Forecast pooling Macro-econometric models Kalman filteringThe typical process of generating a model-based forecast of economic activity involves more than mechanical simulation of a macro-econometric model forward in time. A model-based forecast is conditioned on values supplied for exogenous variables and on assumptions concerning the time paths of policy instruments. In addition, forecasters typically use information outside the model's data base-often from myriad and diverse sources-in formulating their final projection. This information may consist of timely high frequency measurements or data revisions, anticipated events not captured by the model structure, and e\en the predictions of other forecasters. The use of such information to alter a model's 5olution is often termed 'judgemental modification'.In surveying published descriptions of how private forecasters use their models, McNees reported that they attribute anywhere from 20 to 50 percent of the final forecast to the process of judgemental adjustments (1981, pp. 6-7). At the Federal Reserve Board (FRB), the staff outlook is anchored about a consensus projection of the most probable outcome associated with given settings of the policy instruments. As described in Kalchbrenner and Tinsley (1977, pp. 40-44), the consensus projection involves a considerable judgemental component.'' The opinions express'ed are rhose of the authors and do nor necessai-ily rellecr the view, of the Board of Governois of the Federal Reserve System or other mernherc of iis $!aft'.