Twice a year (in spring and in the autumn) the Ifo Institute collaborates with the other institutes or institute consortia to prepare joint forecasts for the world economy and the German economy.
For information on forecasting methods and accuracy refer to the project page: Joint Economic Forecast
The detailed versions of the Joint Economic Forecast are published in ifo Schnelldienst.
Pages with links on summary, detailed version (in German), tables and charts:
Current release
Previous releases
Ifo Project
Topical Terms in Economics
Joint Economic Forecast Spring 2012April 2012