There was a time when only diehard fanatics would bend your ear about the direction of gold prices, but lately investors of all types have discovered a newfound fascination with the yellow metal.

While the perception of gold as a safe haven amid global economic uncertainty has raised the precious metal’s status, gold has also been one of the top-performing asset classes over the past decade.

Indeed, gold is a common-sense portfolio hedge that likely has more upside.

For starters, retail investors aren’t the only ones interested in gold. In the absence of the gold standard, global central banks have been net sellers of gold for decades. But according to data from the World Gold Council and the International Monetary Fund, central banks became net buyers of gold in 2010, purchasing roughly half of global mine production.

And emerging market titans such as China have been particularly aggressive buyers as they’ve worked to enhance their currencies’ credibility and hedge their exposures to the US Dollar.

While central bank buying isn’t likely to last indefinitely, they certainly have plenty of room left to boost gold reserves. According to World Gold Council data, central banks have historically held about 15 percent of their reserves in gold. As of the third quarter of last year, China Shares held just 1.7 percent of its reserves in gold, with India at 9.3 percent and Russia at 8.6 percent. By contrast, the US holds 75.5 percent of its reserves in gold, with Germany coming in at 72.6 percent. That’s a substantial gap that suggests plenty of upside potential.

While holding physical gold has a certain allure, an ex- change-traded product that tracks gold is a far more practical holding for most investors.

With $10 billion in total assets, iShares Gold Trust (NYSE: IAU) is much smaller than its better known peer, SPDR Gold Trust (NYSE: GLD), which has almost $71 billion in assets. Like SPDR Gold Trust, iShares Gold Trust is structured as a grantor trust and its shares are backed by physical gold held in vaults in New York, London and Toronto.

Despite these similarities, there are a couple of key differences between these funds, the most obvious of which is price. Shares of SPDR Gold Trust are each backed by about one-tenth of an ounce of gold, while shares of iShares Gold Trust are backed by one-hundredth of an ounce of the yellow metal. As a result, the share price of iShares Gold Trust is typically one-tenth that of SPDR Gold Shares, though both products mirror the spot price of physical gold with almost no tracking error.

But for investors considering a long-term allocation to gold, the most important difference between the two products is cost. While SPDR Gold Shares charges an annual expense ratio of 0.40 percent, iShares Gold Trust charges just 0.25 percent.

As such, iShares Gold Trust offers investors a cheap alternative to profit from gold’s historic bull market, as global central banks push the yellow metal even higher.