The bond market (also known as the debt, credit, or fixed income market) is a financial market where participants buy and sell debt securities, usually in the form of bonds. As of 2006, the size of the international bond market is an estimated $45 trillion, of which the size of the outstanding U.S. bond market debt was $25.2 trillion.

Nearly all of the $923 billion average daily trading volume (as of early 2007) in the U.S. bond market takes place between broker-dealers and large institutions in a decentralized, over-the-counter (OTC) market. However, a small number of bonds, primarily corporate, are listed on exchanges.

References to the “bond market” usually refer to the government bond market, because of its size, liquidity, lack of credit risk and, therefore, sensitivity to interest rates. Because of the inverse relationship between bond valuation and interest rates, the bond market is often used to indicate changes in interest rates or the shape of the yield curve.

Market structure
Bond markets in most countries remain decentralized and lack common exchanges like stock, future and commodity markets. This has occurred, in part, because no two bond issues are exactly alike, and the number of different securities outstanding is far larger.

However, the New York Stock Exchange (NYSE) is the largest centralized bond market, representing mostly corporate bonds. The NYSE migrated from the Automated Bond System (ABS) to the NYSE Bonds trading system in April 2007 and expects the number of traded issues to increase from 1000 to 6000
Types of bond markets
The Securities Industry and Financial Markets Association classifies the broader bond market into five specific bond markets.

Corporate
Government & agency
Municipal
Mortgage backed, asset backed, and collateralized debt obligation
Funding
Bond market participants
Bond market participants are similar to participants in most financial markets and are essentially either buyers (debt issuer) of funds or sellers (institution) of funds and often both.

Participants include:

Institutional investors
Governments
Traders
Individuals
Because of the specificity of individual bond issues, and the lack of liquidity in many smaller issues, the majority of outstanding bonds are held by institutions like pension funds, banks and mutual funds. In the United States, approximately 10% of the market is currently held by private individuals.

Bond investments
Investment companies allow individual investors the ability to participate in the bond markets through bond funds, closed-end funds and unit-investment trusts. In 2006 total bond fund net inflows increased 97% from $30.8 billion in 2005 to $60.8 billion in 2006. Exchange-traded funds (ETFs) are another alternative to trading or investing directly in a bond issue. These securities allow individual investors the ability to overcome large initial and incremental trading sizes