Vanguard mid cap index fund tracking error

Tracking error is the ultimate measure of judging an index fund manager's performance. Since an index manager does not engage in security selection with an index fund, it is the manager's transactional skill which distinguishes performance. How well the manager uses index futures, cross trading, block trading and manages trading around index reconstitution determines how close the manager can track the index benchmark. Vanguard, in its attempt to closely track index returns, utilizes the following trading policies:
 * Rebalance each portfolio every business day to eliminate or reduce risk factor differences between funds and indexes.
 * Strive to be 100% invested at all times, using futures and ETFs to equitize cash for full investment, with no cash drag and no leverage.
 * Trade carefully, matching execution prices to fund share valuation.
 * Leverage cross-trading opportunities with Vanguard's many other investment funds, reducing or eliminating commissions and transaction charges.
 * Maintain tight controls over commissions, bid-ask spreads, and market impact. For example, our proprietary portfolio systems establish minimum trade sizes to control transaction costs.

Tracking error
Table 1. provides the long term average tracking errors for Vanguard's large cap index funds. (Please note we have data going back to 1993 for the Extended Market fund; the fund began operations in 1987.) With the increased availability of admiral share classes (reduced minimum investment $10,000) we provide tracking error data for both investor and admiral shares. The lower expense admiral shares produce tighter tracking of benchmark returns.

We should note that the historical tracking errors are less than the expense ratios for the funds, meaning that the index manager has provided added returns to fund investors through transactional efficiency. Detailed annual tracking error data (along with additional statistical measurement of fund returns) are provided in the footnote tables.

Benchmark index changes
The Vanguard Extended Market and the Vanguard Mid cap index funds have changed benchmark tracking indices over their history. The Extended Market fund changed from Wilshire to S&P indices; the Mid index fund shifted from S&P indices to MSCI indices. Table 2 provides a breakdown of tracking error to each benchmark index. Since the Mid Cap Index 2003 transition year provided a rather large positive tracking error over the split index tracking index, we have isolated the return in the table. The table also provides the tracking errors since the inception of admiral shares in each fund.