Despite the importance of fiscal policy, a paradox exists. In the case of a government running a budget deficit, funds will need to come from public borrowing (the issue of government bonds), overseas borrowing or the printing of new money. When governments fund a deficit with the release of government bonds, an increase in interest rates across the market can occur. This is because government borrowing creates higher demand for credit in the financial markets, causing a higher aggregate demand (AD) due to the lack of disposable income, contrary to the objective of a budget deficit. This concept is called crowding out. Alternatively, government may increase government spending by funding major construction project. This can also the same project. Another problem is the time lag between the implementation of the policy and detectable effects in the economy. An expansionary fiscal policy (decreased taxes or increased government spending) is usually intended to produce an increase in aggregate demand: however, an unchecked spiral in aggregate demand will lead to inflation. Hence, checks need to be kept in place.