Each month, various professional forecasters give forecasts for next year's real gross domestic product (GDP) growth and unemployment. January is a special month, when the forecast horizon moves to the following calendar year. Instead of deleting the January data when analyzing forecast updates, I propose a periodic version of a test regression for weak-form efficiency. An application of this periodic model for many forecasts across a range of countries shows that in January GDP forecast updates are positive, whereas the forecast updates for unemployment are negative. I document that this January optimism about the new calendar year is detrimental to forecast accuracy. To empirically analyze Okun's law, I also propose a periodic test regression, and its application provides more support for this law.

Additional Metadata
Keywords forecast updates, January effect, Okun's law, periodic regression model, weak-form efficiency
Persistent URL dx.doi.org/10.1002/for.2670, hdl.handle.net/1765/129319
Journal Journal of Forecasting
Franses, Ph.H.B.F. (2020). Correcting the January optimism effect. Journal of Forecasting, 39(6), 927–933. doi:10.1002/for.2670