The average yield to maturity from the HE00 index has compressed to 9.49%, from the wide of 11.97% at the end of November.

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The lower average rating and longer maturity range of the Vanguard index give the fund a higher yield, risk and volatility.

FORBES: Better Bonding

The Vanguard Total Bond Market Index Fund has a yield to maturity of 1.6%, scarcely enough to keep up with inflation.

FORBES: Bond Funds: Higher Yields, Higher Defaults

Yield to maturity on emerging-market debt as measured by the JP Morgan EMBI Global Diversified Index is roughly 5.37%, compared with roughly 2% for the U.S. 10-year Treasury bond.

WSJ: The Allure of Emerging-Markets Bonds

Consider that the Barclays Municipal Bond Index (the most popular industry benchmark) is comprised of predominantly longer-maturity, higher-grade debt.

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The same phenomenon can be observed in the index-linked government-bond market, where both interest payments and the maturity value are pegged to inflation.

ECONOMIST: The remarkable demand for low-yielding government bonds

The auto portion of an ABS index compiled by Barclays has returned 2.34% this year on deals with an average maturity of just over two years.

WSJ: Google Googles 'Higher Yield,' Finds Auto Bonds