Arizona Gov. Doug Ducey signed a law in May to exempt the sale of U.S. gold coins in the state from capital gains taxes.

The measure said taxing a gold coin investment was unfair because the transaction was an exchange of one currency for another. Tax free status would arguably spur investment, but that does not seem to be happening on the large scale.

Sales of gold coins in the first nine months of the year shrank to the lowest in a decade, according to new data from the U.S. Mint. Despite preferential tax status in Arizona, investors are choosing the stock market.

Charles Morgan is editor and a precious metals expert at coinweek.com.

“The same reason they give for the price of metal going up they will give for the price of metal going down," Morgan said. "I essentially think most people should discount what most experts say on the matter. And just understand you don’t have a completely fair or free market on any instrument in the United States and you should only get into precious metals if you are just trying to hold value."

He said in Arizona, where there’s a concentrated population of retirees, that buying gold is an insurance policy of sorts, as a protection or hedge against the ups and downs of investing in the stock market.

Gold coin sales are dropping because buyers would rather put their money in stocks, Morgan said. But, that doesn’t mean the price of precious metals are off in any way.