Good news for people in the market for an engagement ring: A glut of polished diamonds left unsold to Chinese tourists has led to an oversupply in the U.S. market this year.

Tourists drive luxury spending in the U.S. and many American retailers particularly rely on affluent Chinese tourists, who spent an average $6,500 per visitor last year, for their sales. "When the Chinese come to the U.S., they come to shop," Milton Pedraza, chief executive at the Luxury Institute, told CBS News.

But the rising value of the dollar, a slowdown in the Chinese economy, tariff and trade war escalations, and the lack of welcome many Chinese consumers perceive from the U.S. government have cooled tourism between the two countries. Last year, Chinese tourism dropped 5.7% to roughly 3 million travelers, which was the first time Chinese tourism to the U.S. declined since 2003, the U.S. Travel Association said in October.

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Part of the travel jitters have to do with the Chinese government, which through state-sponsored media has warned consumers against flying to the U.S. for work, study or travel, which U.S. Travel President and CEO Roger Dow said over the summer could have a "chilling effect" on travel.

That has meant diamonds, notoriously impervious to price changes, have seen some declines from the lack of demand from consumers and retailers. For example, De Beers, the world's largest diamond company, cut the prices of its rough diamonds by 5% for the first time in years in its November auction to help ease razor-thin margins for diamond retailers, according to Bloomberg News.

Meanwhile, Blue Nile, the largest online jewelry retailer, has reported price declines this year on some stones, typically smaller diamonds popular with Chinese consumers. Katie Zimmerman, chief merchandising officer at Blue Nile, said the online retailer is able to pass on some savings to shoppers thanks to less overhead than traditional brick-and-mortars.

"The decrease does not transfer equally across all stones," Zimmerman said in an email to CBS News. "It is dependent on the stone's size and characteristics (4c's: carat, cut, color, clarity)."

A polished diamond also declines at a lower rate compared to rough stones. If a rough stone falls 8%, prices for the polished diamond may be cut just 3% to 5%, with some falling as much as 7%, Zimmerman said. For shoppers, that means a $5,000 stone could get a discount of roughly $150 to $350.

The lack of spending has resulted in a 3% decline in polished gem prices online this year, according to the Diamond Prices Index.

That spells trouble for American retailers. For example, Tiffany's was sold to LVMH, the largest luxury company in the world, for $16 billion last month after repeatedly blaming poor Chinese tourism spending for stagnating sales this year.

But any retail savings for consumers likely won't last for long, as retailers adjust their expectations and their supply. "The market is now trying to rationalize itself," Zimmerman said. "Suppliers are not going to overproduce by making strong assumptions of the sales."