What Is Factor neutralisation?
Factor neutralisation removes, or constrains, unwanted common-factor exposures from a signal or portfolio. Typical exposures include market beta, sector or industry membership, size, value, momentum, currency, or other style factors. The goal is to assess or trade the signal’s incremental effect rather than a known risk exposure that may dominate its apparent performance.
A researcher can neutralise a cross-sectional signal by regressing it on factor exposures at each date and using the residual, or can build a portfolio whose aggregate exposures are constrained near zero. These approaches answer related but different questions: signal residualisation changes the scores before portfolio construction, while portfolio neutralisation changes the tradable weights. Both require point-in-time factor data and can increase turnover, concentration, or trading costs.
Factor neutralisation does not prove that a signal is independent of all risks or that it will remain neutral after returns move. The factor model, universe, weighting scheme, and constraint tolerances must be reported, and the constrained portfolio should be evaluated separately from the unconstrained result.
See also
Research and literature
Eugene F. Fama and Kenneth R. French, Common Risk Factors in the Returns on Stocks and Bonds, Journal of Financial Economics 33(1), 1993.