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? Our econometric findings are summarized as follows: 1. Governments? budget forecasts are biased in the optimistic direction, especially among the Eurozone countries, especially when they have large contemporaneous budget deficits, and especially during booms. 2. Governments? real GDP forecasts are similarly over-optimistic during booms. 3. Despite the well-known tendency of eurozone members to exceed the 3% cap on budget deficits, often in consecutive years, they almost never forecast that they will violate the cap in the coming years. This is the source of the extra bias among eurozone forecasts. If euro area governments are not in violation of the 3% cap at the time forecasts are made, forecasts are no more biased than other countries. 4. Although euro members without national budget balance rules have a larger over-optimism bias than non-member countries, national fiscal rules help counteract the wishful thinking that seems to come with euro membership. The reason is that when governments are in violation of the 3% cap the national rules apparently constrain them from making such unrealistic forecasts. 5. Similarly, the existence of an independent fiscal institution producing budget forecasts at the national level reduces the over-optimism bias of forecasts made when the countries are in violation of the 3% cap.
Frankel, Jeffrey A., and Jesse Schreger. "Over-Optimistic Official Forecasts in the Eurozone and Fiscal Rules." HKS Faculty Research Working Paper Series RWP12-041, September 2012.