How Third-Party Guarantees Are Quietly (But Significantly) Rewriting the Rules of the Art Auction

The article reports that the New York Spring Marquee auctions in May 2025 generated $1.27 billion, an 8% decline from $1.38 billion in May 2024, followed by a 26% drop in London June auctions to £98 million. In response to this volatile market, auction houses like Christie’s and Sotheby’s are increasingly relying on third-party guarantees (or irrevocable bids), where a buyer agrees in advance to purchase a lot at a set price if no higher bid emerges. Data from Pi-eX Ltd shows that third-party guarantee coverage surged from near zero in 2021 to a record 73% in May 2025, with the Leonard & Louise Riggio collection being 99% backed by such guarantees.