Each quarter, the Federal Reserve Bank of Philadelphia publishes the Survey of Professional Forecasters (SPF). This quarterly survey polls professional economists on their views about the economy over the next few years. Previously conducted by the National Bureau of Economic Research and the American Statistical Association, the survey provides forecasts for nominal GDP and the GDP price index, corporate profits, real GDP and its components, and a number of monthly business indicators, such as interest rates, housing starts, industrial production, and the consumer price index. The Philadelphia Fed has conducted this survey since the second quarter of 1990.

How accurate are the SPF forecasts? On first look, this seems like a straightforward question. The Philadelphia Fed posts the entire history of the survey’s projections on its website, and it is easy to compare these projections with the historical data. On second look, as Dean Croushore and I have noted in our work over the last 10 years, macroeconomic historical data are revised often — and, in many cases, significantly.1 Such revisions complicate the evaluation of forecasts.

In this note, I report on the survey’s accuracy using alternative values of the historical realizations from the Philadelphia Fed’s real-time data set for macroeconomists. I quantify the extent to which the data revisions matter and study the survey’s performance relative to that of simple benchmark time-series models, estimated on the same real-time realizations that the panelists would have used at the time.