If the secret to investing is buy low and sell high, the steep drop in fine wine prices – down between 25 percent and 40 percent from a year ago – could be an opportunity to diversify a portfolio – or not.

“I think there’s plenty of air left in this bubble. There’s more of this drop to come,” economist and author Robin Goldstein said on the sidelines of the American Association of Wine Economists’ (AAWE) annual conference at Princeton University last week.

Some investors are hoping alternative assets like fine wines will net them better returns than those found in the stock and bond markets these days. Studies show that few wines will indeed outperform the S&P 500 over the long term, but the asset class also has great volatility.