Tracking Error
Tracking error measures how much a portfolio's returns deviate from its benchmark. It is the standard deviation of the difference between the two, and it quantifies how much active risk is being taken.
How it is measured
It is calculated on the return difference rather than on the portfolio itself. A portfolio can be volatile and still have low tracking error if it moves closely with its benchmark, and it can be calm in absolute terms while deviating substantially.
The figure is usually annualised and quoted in percentage points. A three percent tracking error means the portfolio's return typically lands within roughly three points of the benchmark in a normal year.
How to read it
Low tracking error means the portfolio closely resembles its benchmark, which limits both underperformance and the possibility of adding value. High tracking error means genuine divergence, in either direction.
The important and counterintuitive property is that active risks do not add up in a straight line. Because separate bets are not perfectly correlated, total active risk is the square root of the sum of the squared individual risks, so combining a three percent and a one and a half percent bet produces about three and a third percent of total active risk rather than four and a half.
A worked example
Running three separate sleeves each with its own budget is not the same as running one large bet. Because the sleeves are imperfectly correlated, the combined active risk is meaningfully lower than the arithmetic total, which is the entire mathematical case for keeping them separate.
The most common mistake
Treating tracking error as a quality measure. It says how different a portfolio is, not how good. A poorly conceived portfolio can have high tracking error and a well conceived one can have low, so it belongs on the risk side of the ledger, never the return side.
How CORVIX uses it
CORVIX runs separate tracking error budgets for its Core, Satellite and Defensive books, so a sector bet cannot silently consume the risk budget allocated to regional conviction. The allocator shows the combined figure computed on the quadrature rule above rather than as a straight sum.
Common questions
What is Tracking Error?
Tracking error measures how much a portfolio's returns deviate from its benchmark. It is the standard deviation of the difference between the two, and it quantifies how much active risk is being taken.
How is tracking error measured?
It is calculated on the return difference rather than on the portfolio itself. A portfolio can be volatile and still have low tracking error if it moves closely with its benchmark, and it can be calm in absolute terms while deviating substantially. The figure is usually annualised and quoted in percentage points. A three percent tracking error means the portfolio's return typically lands within roughly three points of the benchmark in a normal year.
What is the most common mistake when using tracking error?
Treating tracking error as a quality measure. It says how different a portfolio is, not how good. A poorly conceived portfolio can have high tracking error and a well conceived one can have low, so it belongs on the risk side of the ledger, never the return side.