Over the last four decades America's average debt-to-GDP ratio was 39%. At the end of 2007, federal debt was just 35% of GDP. The CBO report says gross federal debt will soar from $17.7 trillion to $27 trillion over the next ten years. CBO warned of the dire consequences the nation's debt will have if gone unchecked. "Such high and rising debt would have serious negative consequences," says the report. "Federal spending on interest payments would increase considerably when interest rates rose to more typical levels. Moreover, because federal borrowing would eventually raise the cost of investment by businesses and other entities, the capital stock would be smaller, and productivity and wages lower, than if federal borrowing was more limited." The report added: "Finally, high debt increases the risk of a fiscal crisis in which investors would lose so much confidence in the government's ability to manage its budge that the government would be unable to borrow at affordable rates."