Most of the art market trades where you cannot see it. Private dealer sales made up $34.8 billion of the $59.6 billion global art market in 2025, according to the Art Basel and UBS Art Market Report, while public auctions accounted for $20.7 billion. So roughly 58% of all art transactions happened away from the auction spotlight, through galleries, advisors, and direct deals between collectors. We spent years and millions of dollars building a reliable index on this asset class, and the lesson we keep coming back to is the one this number makes plain: if you price art off auction records alone, the majority of the market is invisible to you.

How big is the private art sales market compared to public auctions?

The art market runs on two parallel tracks, and the private one is larger. Public auctions, led by Christie's, Sotheby's, and Phillips, are the visible track. Hammer prices get published, archived, and indexed. Analysts build charts from them. Investors study them, including us.

The dealer sector is the other track. In 2025, aggregate dealer sales rose 2% to $34.8 billion, while public auction sales climbed 9% to $20.7 billion. The remaining $4.1 billion came from auction house private sales, a growing hybrid category where houses like Christie's and Sotheby's broker deals behind closed doors using their public auction infrastructure.

Christie's reported $1.5 billion in private sales for 2025, noting that its three biggest transactions of the year all happened privately. Sotheby's posted $1.2 billion in private sales, contributing to its projected $7 billion in total revenue. These figures have roughly doubled since 2019, when Christie's brought in $800 million and Sotheby's about $1 billion from private deals.

Galleries and dealers, meanwhile, remain the most common buying channel. In the 2025 Art Basel survey, 83% of high-net-worth collectors reported buying art at a gallery, whether in person, online, through social media, or at an art fair.

That is it. The headline market most people read about is the smaller half.

How do private art sales actually work?

A private art sale can take several forms, and the simplest is a direct gallery transaction. A dealer has a work, a buyer wants it, and they agree on a price. No public listing, no catalog, no audience.

At a higher level, art advisors broker deals between collectors. Firms like New Perspectives Art Partners, founded by former Christie's chairman Edward Dolman and former Christie's specialist Brett Gorvy, now advise on sales starting at $10 million. They are planning private auctions as in-person events with a small number of invited bidders, where results stay confidential.

Auction houses have built their own private sales divisions. Sotheby's runs dedicated private sale galleries and online platforms. Christie's operates a private sales team that works alongside its public auction calendar. Both make the same pitch to consignors: access to their global buyer network, with the price control and secrecy of a private deal.

New digital platforms are entering too. The Art Marketplace, launched in April 2025 by Elliot Safra, aims to bring some structure to private dealing. In its first three months it brokered sales of works by Basquiat, Kenny Scharf, and Katherine Bernhardt.

The fee structures differ from public auctions, and the difference is worth understanding. In a public sale, buyers pay a premium (typically 20% to 26% at major houses) on top of the hammer price, and sellers pay a commission (often 10% to 15% for high-value lots). Private sales usually involve a flat, agreed-upon fee, often lower than the combined public auction charges. Some dealers work on a net-return basis: the seller agrees to a guaranteed minimum, and the dealer keeps anything above that. These complicated transaction fees are one of the things that inhibit new people from moving into the market.

Why do sellers prefer private sales over public auctions?

Three forces push sellers toward private deals: privacy, price control, and protection from failure.

Privacy matters most at the top end. High-net-worth collectors from the Middle East, Asia, and old-money European families often will not sell publicly for security, tax, or personal reasons. A public auction creates a permanent, searchable record of who sold what and for how much. A private sale does not. In the art market we talk about the 3 D's, death, divorce, and debt, as the moments people sell, and none of them is something a seller wants on a searchable record.

Price control is the second draw. In a public auction, the hammer falls wherever bidding stops. If the market is thin that evening, or if two expected bidders stay home, the seller absorbs the loss. In a private sale, the seller sets a price range and walks away if no buyer meets it. There is no risk of a work "burning," the art-world term for a piece that fails to sell publicly, which can damage its value for years.

The numbers back this up. The unsold rate at public auctions held at 32% in 2025, meaning roughly one in three lots failed to find a buyer. For sellers of major works, that is close to a coin flip with real financial consequences. If a work fails to sell, the auction house may still charge a buy-in fee to cover cataloging and marketing costs, and the piece enters the market with a visible stain on its record.

The growth of third-party guarantees shows how aware the auction world is of this risk. In the first half of 2025, 72.9% of post-war and contemporary works at evening sales carried a house or third-party guarantee, likely the highest level ever recorded. These guarantees shift the downside risk from seller to guarantor, and they also cut into the seller's upside if bidding exceeds the guaranteed floor.

Private sales sidestep all of this. The seller and buyer agree on terms, the work changes hands, and neither price nor identity enters any public database.

Why is the private sales boom a transparency problem for investors?

This is where the private-sales boom becomes a problem for anyone trying to treat art as an investable asset class. Art valuation depends on comparable sales, and a growing share of the comparables are now hidden.

When an investor wants to know what a Basquiat skull painting is worth, the standard approach is to look at what similar Basquiat skulls sold for at auction. Databases like Artnet, Artsy, and Artprice aggregate millions of auction records to make this possible.

But imagine you are that investor and a collector sells a major Basquiat privately for $30 million. That data point never enters the public record. Looking only at auction results, you might see smaller Basquiat works trading for $2 million to $5 million and conclude the market has cooled, when in fact the high end is active and well-priced, and simply hidden.

The scale of this data gap is large. Dealer sales ($34.8 billion) plus auction house private sales ($4.1 billion) total $38.9 billion in transactions that generate little or no public pricing data. That is 65% of the global market operating in the dark.

The Art Basel report itself highlights the tension. Most collectors surveyed said that more transparent pricing would make buying easier. Yet fewer than half of galleries (44%) display prices online for all available works, and 25% share prices only on request. Among collectors who bought art online in 2024, 48% cited "not enough information about the work" as a major barrier, and 43% pointed to the lack of visible pricing.

For investors used to the structured data of equity or bond markets, this opacity is a serious structural gap. There is no Bloomberg terminal for art. The closest thing, auction records, covers only about a third of the market by value. That gap is precisely the inefficiency that makes the asset class interesting, and it is also the part you have to respect before you allocate a dollar.

What does the private-public split mean for art investors?

Investors weighing art as an alternative allocation should factor in three things about the private-public split. We would frame each in plain investing terms.

First, auction-based indices undercount the market. Indices built on public auction data, like the Artnet Price Database or the Mei Moses All Art Index, track only the visible slice. They miss the $38.9 billion in private transactions that could tell a very different story about price trends, especially at the high end where private dealing is most common.

Second, valuation without private sale data can mislead you. A gallery might sell a masterpiece for millions with no public trace, while the same artist's smaller works trade modestly at auction. Working from data alone, you could read this as a declining market, when the true demand picture is more complex.

Third, the shift toward private sales is still accelerating at the institutional level. Christie's private sales have nearly doubled since 2019. New firms like New Perspectives Art Partners are building entire businesses around private dealing for works above $10 million. Pace Gallery partnered with former Sotheby's private sales head David Schrader to launch Pace Di Donna Schrader in early 2026, focused entirely on secondary-market private deals.

There is a flip side worth naming. For platforms that aggregate large datasets across both public and private channels, this shift may create an edge. The investors with the best access to private sale records, whether through proprietary databases, dealer relationships, or art advisory firms, will have the most accurate read on where prices really stand. We think the data advantage compounds in a market this opaque.

The Bottom Line

  • Private dealer sales ($34.8 billion) and auction house private sales ($4.1 billion) together made up 65% of the $59.6 billion global art market in 2025, dwarfing public auction revenue of $20.7 billion.
  • Sellers choose private sales for three main reasons: confidentiality, control over pricing, and protection from the reputational damage of a failed public auction.
  • Christie's and Sotheby's have roughly doubled their private sales volumes since 2019, signaling that even the auction giants see the future in closed-door deals.
  • Auction-based art indices and databases capture only about a third of market activity by value, creating a significant blind spot for data-driven investors.
  • Investors assessing art should seek sources that combine public auction data with private sale intelligence, or accept that their pricing picture is incomplete.

Sources

  1. Art Basel and UBS. "The Art Basel and UBS Global Art Market Report 2026." Art Basel, March 2026. https://www.artbasel.com/stories/the-art-basel-and-ubs-global-art-market-report-2026
  2. The Art Newspaper. "Christie's and Sotheby's end 2025 with increased sales, thanks to luxury goods, trophy lots and private deals." December 2025. https://www.theartnewspaper.com/2025/12/17/christies-and-sothebys-end-2025-with-increased-sales-thanks-to-luxury-goods-trophy-lots-and-private-deals
  3. Artnet News. "Dark Mode: Inside the Art Market's Private Auction Playbook." 2025. https://news.artnet.com/market/intelligence-report-art-market-private-auction-playbook-2757275
  4. Artnet News. "Art Dealers Report More Sales in 2025, But Fewer Buyers." 2025. https://news.artnet.com/market/art-dealer-sales-2025-2754173
  5. Maddox Gallery. "Behind Closed Doors: The Shift from Public Auctions to Private Art Sales in the Global Art Market." 2025. https://maddoxgallery.com/news/431-global-art-market-shift-public-auctions-to-private-art-sales/
  6. Art Basel. "Six art market trends to watch in 2026." 2026. https://www.artbasel.com/stories/art-market-trends-watch-2026-experience-digital-middle-east-private-sales
  7. Bank of America Private Bank. "Fall 2025 Art Market Update: Analyzing Current Trends." 2025. https://www.pbig.ml.com/articles/art-market-fall-update.html
  8. ARTnews. "After Two Years of Decline, the Art Market Edges Back to Growth, Says 2026 Art Basel UBS Report." 2026. https://www.artnews.com/art-news/news/art-market-report-2025-growth-high-end-sales-1234777143/
  9. Artnet News. "Inside the Art Marketplace: A New Private Sales Platform for Collectors." 2025. https://news.artnet.com/art-world/the-art-marketplace-private-sales-2738131
  10. Sotheby's. "Sotheby's Projects 2025 Consolidated Sales of $7 Billion." December 2025. https://www.sothebys.com/en/articles/sothebys-projects-2025-consolidated-sales-of-7-billion