Quartz did an admittedly targeted survey of “the holdings of 20 museums in 7 countries, focusing on the work of 13 major artists” to see how much of the work owned by the museums was on display. As the post explains, there are some important nuances to these display rates, like the the National Gallery which has a huge body of Rothko’s work and the place where much of it would be displayed is being renovated.
Nonetheless, the survey reminds us why big institutions have so much art and that they cannot display it all:
Artists, collectors, and foundations donated the vast majority of the art represented in this survey. In addition to the potential tax write-off, benefactors often view large museums as the only places that can guarantee important works of art will be properly conserved. They may also seek out institutions that have a policy of never selling the work, as the Rothko Foundation did with the NGA. As a result, art tends to accumulate in the storage vaults of big museums rather than the galleries of smaller ones.
Moreover, the roughly 5% of their collections that museums do display is usually rotated among the most culturally important works they have. Less significant or niche works may never leave the archives except to be conserved. A 2002 dissertation found that at the Fine Art Museums of San Francisco, which are included in our survey, donated items were displayed much less frequently than purchased ones.