Definition of 'Benchmark Error'
A situation in which the wrong benchmark is selected in a financial model. This error can create large dispersions in an analyst or academic's data, but can easily be avoided by selecting the most appropriate benchmark at the onset of an analysis.
Investopedia explains 'Benchmark Error'
When creating a market portfolio under the capital asset pricing model (CAPM), it is important to use the most appropriate benchmark, or market, in your calculations. If, for example, you want to create a portfolio of American stocks using the CAPM, you would not use the Nikkei - a Japanese index - as your benchmark.
Accordingly, if you want to compare your portfolio returns, you should use an index that contains similar stocks. For example, if your portfolio is tech-heavy, you should use the Nasdaq as your benchmark, rather than the S&P 500.