Something to add to the debate regarding the proposed resale royalties scheme: a bill has been put before the US Congress (for the fifth time) that would allow artists who donate their work to museums or libraries to deduct the fair market price from their taxes. Currently, collectors who donate art works to public institutions can make this deduction, but artists can only claim the costs of materials.
Bill encourages artists' donations (again) - The Art Newspaper
Interestingly, artists' right to a deduction was revoked in the US in 1969 after some artists were caught inflating the value of their donated works.
In New Zealand, there are no tax incentives for anyone to donate art works to public collections.