In the past, Zero Hedge has noted the correlation between Sotheby's (BID) and the S&P. It has been a pretty good "bubble" barometer over the last couple decades. As cheap money tries to find places to play, Sotheby's has boomed and/or contracted in exaggerated synchronicity with the "wealth effect" of a given period. In the chart below, the blue line is the S&P and the black is BID.
Given its past correlation, I like to periodiocally check in on its status. What I thought worth noting is that in the recent ramp, while the S&P pushed to new intermediate highs, BID did not. In fact, much like parts of the commodity complex, BID has remained in a clear downtrend.
Extrapolate from that what you will, but one thing does appear clear: BID buyers are feeling less hopeful than SPY buyers. And it's worth noting that in both 2000 and 2008, BID peaked and/or pushed to aggressive new lows well before the broader market.