(Wine-Searcher) - A smaller harvest means prices for top-end California wines will keep on rising.

After a smaller harvest and with a strong economy, Napa Cabernet prices should go up over the next year, a leading California wine industry banker predicts.

This may not sound like news, products going up in price. But in the high-end wine industry, prices don't really reflect the costs of materials. It's all about brand value and, to a lesser extent, supply and demand. All of these factors are working in favor of Napa Cabernets, says Rob McMillan, executive vice president of Silicon Valley Bank.

Silicon Valley Bank is in the middle of collecting results from its annual Wine Conditions Survey. California wineries report the size of their harvest, and also whether they plan to raise prices. So far, many Napa Valley wineries have said they are planning to increase prices, McMillan told Wine-Searcher.

"You have to look at the economy and say: 'Is that going to work?'" McMillan said. "The views of the producers suggests that they believe it can."

Sales data from Nielsen shows that Americans are continuing to spend more money on wine, with wines priced at more than $15 increasing fastest in sales, while sales of wines priced less than $9 are actually dropping.

Some high-end California wine producers have held the line on serious price increases for several years. After the '08 economic crisis, many wineries found themselves with wines priced higher than distributors wanted to handle. By the time the economy righted itself, they had to deal with a 2011 harvest that wasn't highly regarded by some critics, and then record harvests in 2012 and 2013, which skewed the supply-demand relationship. The 2014 harvest, while smaller than the two before it, was still the third-largest harvest in California history.

But 2015, after several years of drought, appears to have brought significantly smaller harvests across most of California. While there's still plenty of wine in the distribution chain – "You can look around and find lots of '12s right now," McMillan says – the impression of impending scarcity may be as important for pricing as actual scarcity.

"It's pretty easy to find anything else you want right now," McMillan says. "If there is something in short supply, it's good quality Napa Cab."

McMillan says that harvest conditions and prices elsewhere, such as in Bordeaux, have little to no impact on prices in Napa.

"They're different wines, totally different," he said. "At the very top end, they're luxury products, and it depends on how you brand them. And the Bordelais continue to give (Napa producers) some headroom to grow with their first-growth prices."

But international conditions do make a big impact on other California wines. And, unfortunately for the San Joaquin Valley growers who make the majority of wine consumed in the US, the economic conditions are looking quite the opposite of those in Napa Valley, McMillan says. The drought led to smaller yields, and international competition in the $10 and under range has driven down prices for grapes. Moreover, the option of pulling up vineyards and planting nut trees – which many grapegrowers have done over the last decade – isn't appealing right now because nut trees use much more water than grapevines.