Tracking Difference & Error: Evaluating Hidden ETF Costs

The Total Expense Ratio (TER) is the most well-known metric when buying an ETF. It indicates how much the ETF provider deducts annually as a fee. The TER is important, but often deceptive because it does not include trading costs (transaction costs) within the fund or revenue from securities lending.

To assess the actual quality and true costs of an ETF, institutional investors look at two other metrics.

1. Tracking Difference (TD)

• If the Tracking Difference is negative (e.g., -0.15%), the ETF was 0.15% behind its index.
• The trick: Some ETFs have a positive Tracking Difference! Despite the TER, they achieve a slight outperformance compared to the index because the ETF provider generates additional returns through securities lending or clever tax optimization.
• An ETF with TER = 0.20% and TD = -0.05% is ultimately cheaper and better performing than an ETF with TER = 0.12% and TD = -0.30%!

2. Tracking Error (TE)

The Tracking Error measures the volatility of the Tracking Difference. It indicates how much the daily fluctuations of the ETF deviate from the daily fluctuations of the index.
• A low Tracking Error means that the fund extremely reliably and consistently draws exactly the same curves as the index.
• A high Tracking Error indicates sloppy management or flawed, inaccurate sampling. Investors must expect incalculable, sudden deviations.

Summary: The TER is the marketing indicator, Tracking Difference is the return destroyer (or savior), and Tracking Error shows management quality.