Vanguard municipal bond fund tracking error

Tracking error is one means of measuring active manager performance against an appropriate market index. Vanguard's national Municipal bond funds are actively managed, defined asset class funds. The funds include four municipal bond funds  structured across four bond maturity levels: short, limited, intermediate, and long term bonds. In addition to these four portfolios, Vanguard manages state specific municipal bond funds and a high yield municipal bond fund. The municipal bond market is a very large market, with many illiquid securities. The following table shows the number of securities held by the funds and by municipal bond benchmark indices. The comparative indices include the Barclays Capital 3 Year Municipal Bond Index; the Barclays Capital 7 Year Municipal Bond Index; and the Barclays Capital 10 Year Municipal Bond Index; the broad market is represented by the Barclays Capital Municipal Bond Index.

Tracking error
Table 2. provides long term average tracking errors for Vanguard's Municipal bond funds. Data extends from 1993 to present for the Short, Limited, Intermediate, and Long term Municipal fund investor shares. Admiral share class data covers the period from 2002 (the first full year of operations of the share class) to the present. Detailed annual tracking error data, along with additional statistical measurement of fund returns, are provided in the footnote tables.

The relative performance of investor and admiral share classes can be best illustrated by viewing performance over a common holding period. The following table examines the average tracking error performance of each fund over the period beginning with the first full year of admiral share performance to the present. The lower expense admiral shares provide for lower tracking errors to benchmark performance.

Over the 1993 to the present, the funds have realized average tracking errors in excess of the annual management expense ratio (0.20%). Vanguard, in its annual reports, has reported the "most comparative benchmark" for each of the funds since 2000. One should note that the short term municipal fund and the limited term municipal fund are benchmarked to the same index, the Barclays Capital 3 Year Municipal Bond Index. The short term fund holds securities with average maturities of slightly more than one year, so its duration and yield is lower than the index. The lower comparative yield is the major factor in the fund's large tracking error. The limited, intermediate, and long term funds have durations that shift modestly from the benchmark durations (nearly half slightly longer, half slightly shorter). The average duration difference is 0.1 to 0.2 years, which translates into an average 10 to 20 basis points of tracking error (see tab four "duration" in the footnote tables for comparative duration figures). In addition, the funds do not precisely match the correlation (r-squared) and volatility (beta) of benchmark indices (see the duration tab in footnote tables for annual data).

Tracking error has been volatile and considerably high over the 2008-2010 financial crisis period. The 2008 financial crisis was marked by the following disruptions in municipal market fundamentals:
 * 1) In 2008, first a freezing up of funding in the auction-rate securities market, followed by the downgrading to junk status of most municipal bond insurers, with a coincident downward repricing of insured municipal bonds (in response to the virtual disappearance of bond insurance, Vanguard merged it's insured long term municipal bond fund into its long term municipal bond fund on December 12, 2008.)
 * 2) Late in 2008,  large sales imbalances in the marketplace due to institutional selling of municipal securities to meet obligations backed by defaulted mortgage securities;
 * 3) In 2010 a surge in supply of new municipal securities due to the impending termination of the Build America Bond program.