“Long-term returns, particularly at the high end of the market, continue to perform well relative to many other asset classes, which is driving up prices. According to Knight Frank’s Wealth Report 2013, art has seen a 92 per cent increase in value over the past five years and a 199 per cent increase over ten years.”
See the article at: http://www.ft.com/intl/cms/s/0/007144de-be3c-11e2-9b27-00144feab7de.html#axzz2TVZEdrOL
Helmar Sports Cards and Baseball History 