What is the main purpose of the 'acting in concert' concept in takeover regulation?

The 'acting in concert' concept in takeover regulation is primarily designed to group together parties that are presumed to be cooperating in relation to takeovers or actions that may prevent a takeover. This concept is crucial because it addresses situations where multiple parties might work together to influence the outcome of a takeover bid, such as coordinating their votes or sharing information, even if they are not formally organized as a single entity.

By defining who is acting in concert, regulators can enforce disclosure requirements and ensure that the true extent of control or influence in a takeover situation is revealed to the market. This helps maintain a level playing field for all investors, as it prevents covert arrangements that could unfairly alter the dynamics of the acquisition process.

The other options do not capture the essence of this concept. For instance, joint advertising campaigns do not pertain to regulatory concerns about control or influence in takeovers. Similarly, simplifying the purchase of securities for individual investors and enhancing transparency in market dealings focus more on other aspects of market regulations rather than the specific dynamics of coordinated actions in takeover situations.