On 19 November 2024, the Financial Conduct Authority (FCA) published a research note in which it reviews the methodology for calculating its market cleanliness statistic (MCS), which is used in its annual report to measure insider trading. The MCS is based on abnormal stock price movements before takeover offer announcements.

The FCA plans to amend its methodology to improve the coverage and robustness of the MCS. It explains that the new methodology will incorporate intraday trading activity and lead to a statistic that is robust to periods of heightened market volatility. Its aim in making these adjustments is to ensure that the MCS supports the FCA in setting high standards of transparency, reducing the risk of market manipulation and promoting healthy competition.

The MCS will be published according to the new methodology with effect from 2024. The FCA notes that it welcomes feedback on the revised methodology and findings set out in the research note.