the period during which it is not possible to carry out a specific operation. The reasons behind, and characteristics of, these "closure periods" vary according to the type of product. For example, in initial public offerings (IPOs) some shareholders can sign a lock-up commitment, which obliges them to hold their shares for a certain period; the aim of this is to facilitate the shares' placement among the public, eliminating uncertainty and the decrease in prices that would occur if any significant shareholder chose to dispose of their shares. In the field of investment funds, the lock-up is the period during which the entry of new participants or the execution of additional investments in a fund is prohibited (usually the case in hedge funds, if established in the fund statement); the reason for this closure is that the fund would have already reached the volume of assets suitable for efficient management and a further increase could, in the manager's opinion, result in a lower expectation of returns among the shareholders.