The Art Institute of Chicago acquires hundreds of artworks each year, but how these masterpieces enter the museum’s collection is not generally public knowledge. Once a year, however, this process becomes fascinatingly transparent.

On May 20, about 200 art collectors will gather at the Art Institute to decide which of five finalist artworks will join the museum’s renowned collection. These finalists are already on public view in a gallery in the Modern Wing. They include contemporary artworks made by American and European artists between 1974 and 2013.

The art collectors, part of a membership group called the Society for Contemporary Art, raise money every year with a benefit art auction and party. The proceeds fund an art purchase.

The Society for Contemporary Art is pay-to-play; anybody can join (the lowest annual rate is $150) and cast a vote during the upcoming art election. “You get to decide how the money is spent,” David Egeland, the group’s vice president of acquisitions, told Chicago. “You have some influence on what ends up in the museum.”

It turns out the group has a prestigious history. The museum’s Jackson Pollock drip painting, for example, won the vote in 1955. Egeland says the group paid $2,500 for it; today, it could sell for eighty million dollars.

This year’s crop includes a mix of emerging and established artists. The most rare artwork is Bas Jan Ader’s Piet Niet, from1974. The Dutch conceptual artist is best known for his final artwork, in which he attempted to cross the Atlantic Ocean in a small boat. He was lost at sea. Ader created Piet Niet one year before his death. It is perhaps the only painting that he ever made.

Although the collectors aren’t allowed to say how much the artworks cost, or how large their treasury is, Egeland told Chicago that this year’s benefit was so successful they will be allowed to purchase two artworks for the museum. “Sometimes, even, a member gets excited and buys an artwork that didn’t make the vote, and donates it to the museum,” said Egeland.

The remaining artworks under consideration are Jo Baer’s Memorial for an Art World Body (Nevermore), 2009; Michael Buthe’s Untitled, 1989–93; William Leavitt’s Manta Ray, 1981; and Mathias Poledna’s Imitation of Life, 2013.

The acquisition finalists are on view in the Modern Wing at the Art Institute of Chicago through August 3.