According to the work of Olivier Chanel at Marseilles' Groupement de Recherche en Économie Quantitative d'Aix-Marseille (GREQAM), art prices lag equity markets by around a year or so which number matches the experience of most attentive observers.
*I just had an argument that U.S. market valuations are no longer as correlated as global market cap.
Another approach would be to look at the largest marginal buyer. As an example, the art market peaked in 90-91 after the Japanese market top-ticked in Dec. '89 rather than after the U.S. market highs of August 1987.
Going with the first alternative, world market cap peaked at ~$71 trillion in May 2015 and appears to have bottomed at ~$56 trillion on Feb. 11, hence the new, super-valuable answer of 'maybe'.
From the Daily Mail:
Have art prices PEAKED? Auction houses report falling profits as the value of even Picassos tumble
- Auctions by Sotheby's and Christie's bring in 45% less than the year before
- Picasso's Tete de Femme sold for £10m less in January than it did in 2013
- Drop in prices blamed on macho 'willy waving' by auction house bosses