The callable capital pledged by the 22 non-borrowing members, which include the world's wealthiest developed countries, therefore functions as a guarantee for the bonds that the IDB sells. This arrangement ensures that the IDB maintains a triple-A credit rating, and as a result can make loans to its borrowing member countries at rates of interest similar to those that commercial banks charge their largest corporate borrowers. At the same time, the 22 non-borrowing countries are only putting up guarantees – not actual funds – so their support of the IDB's lending operations has a minimal impact on their national budgets.