Sharpe ratio meaning

In legal practice, the Sharpe ratio is used to express a fund or portfolio’s risk‑adjusted return in due diligence, fund prospectuses, investment management agreements, and performance fee or benchmark provisions. It measures the average additional return per unit of risk: specifically, the average return in excess of the risk‑free rate divided by the volatility (standard deviation) of that excess return over the chosen period. The risk‑free rate is typically a cash proxy or short‑dated government security (for example, UK Treasury bills, SONIA, or short‑dated gilts in England & Wales, Scotland and Northern Ireland; and euro area Treasury bills or €STR in Ireland). Usage and meaning are broadly consistent across these jurisdictions, though the proxy selected may differ. The term is not defined in legislation or case law; it is a widely used financial metric that informs regulatory disclosures (e.g. under FCA and Central Bank of Ireland rules), marketing communications, and suitability assessments. Its practical significance lies in comparing managers and strategies on a like‑for‑like, risk‑adjusted basis. Care is needed: the measurement period, return frequency and risk‑free proxy can materially affect the ratio. It is backward‑looking and penalises upside as well as downside volatility. Methodology should be disclosed to avoid misleading statements.