In the straw poll, Wendy Cooper asked for more explanation. She "would like to know reasons for not paying the pre-existing licenses after withdrawal".

Our reasoning was that members should share in the consortium income. Withdrawn members are honoring their contractual agreement to allow certain works to remain in limited licenses for limited times after their withdrawal, but calculating what part of the income pertained to these would be exceptionally complex. In addition, the idea is to discourage museums from withdrawing. This is fairly common in most situations in the world - officers of a corporation may be entitled to bonuses if they stay to the end of the year, but if they leave the firm in November they won't get them, etc.

In effect, members own shares. If you leave, you give up your accumulated shares. David