This article assesses the effectiveness of UK age discrimination law in protecting older workers from claims that such workers are less productive and perform more poorly than younger workers. The article assesses employer perceptions and the incompatibility of such perceptions with existing research and the current interpretation of age discrimination law by the CJEU and the Supreme Court which accords with such research. The effectiveness of age discrimination law in practice is assessed through an analysis of existing compensation reduction rules. The article concludes that the existing rules which allow for a reduction in compensation payable where there is a chance that the same outcome would have been reached in the absence of discrimination ( â€˜chance modelâ€™) reduces the effectiveness of the existing protections. A move to a â€˜certainty modelâ€™ would be less speculative, would serve the objectives of anti-discrimination law and would reduce concerns about compatibility with EU law.