An investor who prefers to invest half of available funds in the S&P 500 and half in mid-cap stocks is following a certain investing style, and that manager's results can be attributed in part to how well the S&P 500 and mid-cap stocks in general perform. It can be useful to have an independent way of determining what investment style a manager is using and how much of the resulting return variation is a consequence of the style as opposed to such factors as stock selection.

BIRR provides a method of Style Analysis that depends only on historical returns. This means that any stock portfolio, or any asset, can be analyzed, even if no specific information about the intended investment style is available. The method used builds on ideas proposed by William F. Sharpe in his paper "Asset Allocation: Management Style and Performance Measurement" published in The Journal of Portfolio Management, Volume 18, Number 2 (Winter 1992), pages 7-19.

BIRR Style Analysis operates by comparing the returns history of a set of style benchmarks with the returns of the asset you have selected for analysis. Using a fast non-linear optimization algorithm, the BIRRŪ Performance Analyzer determines the relative investment weights for these style benchmarks that would result in an equivalent style portfolio whose returns most closely match the variation in returns for the selected asset. The results can be viewed in a text report or graphically.