It is quite refreshing to know that foreign governments only own a quarter of our $8.5 trillion national debt.

The money flows in from all over the place: from individual investors and corporations, pension funds and governments, both in the U.S. and around the world. Basically, anyone with a large amount of cash looking for a safe place to put it is a good candidate for holding U.S. Treasury debt.

So just who are these lenders? As of last June (the latest complete breakdown available), the biggest holder of Treasury debt was the U.S. government itself, with about 52 percent of the total $8.5 trillion in paper that's out there. Most of the government’s holdings are massive savings accounts for programs like Social Security and Medicare. Just as you may prefer to keep your Individual Retirement Account in the safe Treasury bonds, the folks who manage the Social Security Trust Fund are looking for a secure investment, too.

That’s leaves a little over $4 trillion in public hands. The biggest chunk (about 25 percent of the $8.5 trillion total) is held by foreign governments. Japan tops the list (with $644 billion), followed by China ($350 billion), United Kingdom ($239 billion) and oil exporting countries ($100 billion).

Other big holders of Treasury debt include state and local governments ($467 billion); individual investors, including brokers ($423 billion); public and private pension funds (319 billion); mutual funds ($243 billion); holders of US savings bonds ($206 billion); insurance companies ($166 billion) and banks and credit unions ($117 billion.)