What Is Tracking error?

Tracking error, also called active risk, measures how much a portfolio’s returns vary relative to a chosen benchmark. It is the standard deviation of the period-by-period differences between portfolio and benchmark returns, often annualised for reporting:

Tracking error = standard deviation(portfolio return - benchmark return)

A higher value means greater variability of benchmark-relative returns; it does not say whether the portfolio tends to outperform. Tracking error is also distinct from the average return gap or the largest single-period deviation. Comparisons require the same benchmark, return frequency, measurement window, and annualisation convention.

For portfolio construction, calculate tracking error on the whole portfolio against its intended allocation benchmark. A portable alpha or return stacking overlay can differ greatly from the benchmark as a standalone line item, yet have a smaller effect on total-portfolio tracking error when it is modestly sized or diversifies other holdings. Conversely, hidden market exposure or correlated losses can increase the portfolio’s active risk. The Peter Hecht podcast episode discusses this distinction when assessing portable-alpha allocations.

Further reading:

• CFA Institute — Investment Performance Measurement.

• Peter Hecht episode notes — Portable Alpha: Solving the Funding Problem of Alternatives.

See also

• Benchmark

• Portfolio construction

• Risk-adjusted return

• Portable alpha

• Line item

• Market exposure

• Beta overlay