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.
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.
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.
But participants who buy and sell bonds before maturity are exposed to many risks, most importantly changes in interest rates. When interest rates increase, the value of existing bonds fall, since new issues pay a higher yield. Likewise, when interest rates decrease, the value of existing bonds rise, since new issues pay a lower yield. This is the fundamental concept of bond market volatility: changes in bond prices are inverse to changes in interest rates. Fluctuating interest rates are part of a country's monetary policy and bond market volatility is a response to expected monetary policy and economic changes.
Economists' views of economic indicators versus actual released data contribute to market volatility. A tight consensus is generally reflected in bond prices and there is little price movement in the market after the release of "in-line" data. If the economic release differs from the consensus view the market usually undergoes rapid price movement as participants interpret the data. Uncertainty (as measured by a wide consensus) generally brings more volatility before and after an economic release. Economic releases vary in importance and impact depending on where the economy is in the business cycle.