Hackett said if the stock market falls further, that could put more pressure on ETFs as those investors view their gold holdings as a stock and not necessarily a physical holding.

FORBES: FOCUS: Falling Commodity Prices, Slowing Global Growth Stir Deflation Thoughts

The physical economy and the one represented by the stock market in the U.S. rarely match.

FORBES: In Brazil, Strong Labor Market, Weak Economy

Chains with physical stores such as Wal-Mart are more likely to go out of stock on some products than online retailers such as Amazon.

FORBES: Amazon's Showrooming Effect And Quick Growth Threaten Wal-Mart