Modern antitrust enforcement is based on a clear and objective assessment of effects as identified or measured by sound economic analysis. Agencies and courts across the OECD, however, display varying degrees of sophistication when dealing with economic analyses. Reasons why courts reject economic evidence include exacting standards of proof, a lack of guidance from the authorities, a lack of understanding by the judges and ineffective presentation by the competition authorities. Various techniques are used in court to help judges understand complex economic evidence. Some of them proved more effective than others, particularly if their purpose is to make complex concepts easily accessible to non-experts and to present them in a plain and clear way.