Over-optimistic Official Forecasts in the Eurozone and Fiscal Rules

Why do countries find it so hard to get their budget deficits under control? Systematic patterns in the errors that official budget agencies make in their forecasts may play an important role. Although many observers have suggested that fiscal discipline can be restored via fiscal rules such as a legal cap on the budget deficit, forecasting bias can defeat such rules. The members of the eurozone are supposedly constrained by the fiscal caps of the Stability and Growth Pact. Yet ever since the birth of the euro in 1999, members have postponed painful adjustment by making overly optimistic forecasts of future growth and budget positions and arguing that the deficits will fall below the cap within a year or two. The new fiscal compact among the euro countries is supposed to make budget rules more binding by putting them into laws and constitutions at the national level. But what is the record with such national rules?