Outside the United States, many other countries in the world also issue similar bonds, sometimes called local authority bonds or other names. The key defining feature of such bonds is that they are issued by a public-use entity at a lower level of government than the sovereign. Such bonds follow similar market patterns as U.S. bonds. That said, the U.S. municipal bond market is unique for its size, liquidity, legal and tax structure and bankruptcy protection afforded by the U.S. Constitution.