Bloomberg Barclays US Aggregate Bond Index

The Barclays US Aggregate Bond Index (ticker: LBUSTRUU), formerly the Lehman Aggregate Bond Index, was created in 1986 with backdated history going back to 1976. The index is a predominate index benchmark for US bond investors, and is a benchmark index for many US index funds.

Overview
The Index is a composite of four major subindexes: US Government Index; US Credit Index; US Mortgage Backed Securities Index (1986); and (beginning in 1992) US Asset Backed Securities Index. The index holds investment quality bonds. The ratings are based on S&P, Moody, and Fitch bond ratings. Table 3 in the appendix provides credit quality breakdowns for the index from 2005-2009. The index does not include high yield bonds, municipal bonds, inflation-indexed bonds, or foreign currency bonds. In 2010, the index held more than 8,200 bond issues. The time line for the addition and subtraction of asset classes, as well as changes in the minimum issue size and credit quality standards for the index are included in the time line sidebar.

The current bond asset classes comprise the index:


 * 1) Government
 * 2) Treasury bills, notes, and bonds
 * 3) Agency bonds
 * 4) Credit
 * 5) Industrial
 * 6) Finance
 * 7) Utility
 * 8) Yankee Bonds
 * 9) Mortgage Backed
 * 10) GNMA
 * 11) FNMA
 * 12) FHLMC
 * 13) Asset backed
 * 14) Credit card receivables
 * 15) Auto Loans
 * 16) Home equity loans

The relative weighting of asset classes within the index changes over time as new asset classes are added to the index, as issuance of bonds grows and ebbs, and as market security values fluctuate. The following table shows the index sector allocation over the period 1973-2009. A breakdown of mortgage backed securities (GNMA, FHLMC, FNMA) in the index from 1978-2001 is included in Table 4. of the appendix. In June 2009, as a result of the 2008 financial crisis, Barclay's announced the creation of the US Aggregate Float Adjusted Index that excludes Treasuries, agencies and MBS held in Federal Reserve accounts.

Credit quality
The table below shows the annual distribution of credit quality holdings in the index.

Index returns
The following table provides return data for the index.



Index funds
The Barclays US Aggregate Bond Index was formulated as a market benchmark and contains thousands of illiquid bonds. Index fund managers therefore use sampling strategies when attempting to construct index funds tracking the index. Bond holdings range from approximately 800 to 1600 bonds for SPDR and Ishares  ETFs; and from approximately 930 bonds (TRowePrice) to 5200 bonds (Vanguard) for bond index mutual funds. The Vanguard Bond Market ETF is a share class of the Vanguard bond market index fund.