A recent article in the WSJ cited John Maynard Keynes’s art collecting prowess stating that he achieved an average annual return of 10.9%:
In his three decades of collecting, Keynes paid a total of £12,847 for his holdings, roughly £600,000 ($840,000) today when adjusted for inflation. Based on appraisals in 2013 by five independent experts, Keynes’s collection is worth more than £70.9 million, or $99 million.
The article also does a very good job of pointing out that overall success was achieved through a small handful of pieces in the collection: “Of the 135 works in Keynes’s collection, two account for more than half its total value and 10 constitute 91%.”