How Accurate Have Congressional Cost Estimates Been Historically?

How have the bureaucrats in Congress performed historically when they announce that they will save money with one of their programs or entitlements? If the historical record shows that in every case, Congress has dramatically underestimated the cost of a new program or entitlement, wouldn't you be reluctant to believe them now? If cost savings and efficiencies are being promised by people like Nancy "Natural Gas Is Not A Fossil Fuel" Pelosi and Charlie "Taxes Are For Little People Who Don't Have Buildings In Harlem Named After Them" Rangel, would you take their word for it?

A few days stale, but good stuff from the Wall St. Journal:

Washington has just run a $1.4 trillion budget deficit for fiscal 2009, even as we are told a new health-care entitlement will reduce red ink by $81 billion over 10 years. To believe that fantastic claim, you have to ignore everything we know about Washington and the history of government health-care programs. For the record, we decided to take a look at how previous federal forecasts matched what later happened. It isn't pretty.