The Sonoma County wine industry plays an increasingly important -#8212; and surprisingly large -#8212; role in driving the local economy, according to an industry-funded report issued Thursday.

The study, conducted by Stonebridge Research Group, estimates that wineries and grape growers contributed $13.4 billion to the local economy in 2012, including direct and indirect impacts.

The numbers in Thursday's report suggest the wine industry's economic impact dwarfs other sectors. The entire Sonoma County economy was pegged at $20 billion in 2012, according to a report issued last fall by Moody's Analytics, which supplies regional data to the county Economic Development Board.

The wine industry and wine-inspired tourism would account for two-thirds of that number, according to the report compiled for the Sonoma County Vintners and Sonoma County Winegrowers. The results were announced Thursday at the Sonoma County Vintners' annual meeting.

"I didn't know what to expect, because I hadn't gone through the numbers," said Honore Comfort, executive director of Sonoma County Vintners. "I was fully expecting growth, but I wasn't certain, so we're thrilled."

The results released Thursday were preliminary, and a fuller picture will emerge over the next few weeks, she said.

Karissa Kruse, president of Sonoma County Winegrowers, said she's looking forward to digging into the full report to dissect what's driving the growth.

"It's really important to demonstrate back to the community the value of the wine industry, especially the jobs," Kruse said.

The report suggests the economic impact of the wine industry has grown dramatically since 2005, when a similar study estimated the industry generated $7.6 billion in direct and indirect economic activity.

"That does not surprise me," Comfort said. "There are so many more wine tasting rooms than there were in 2005. Barrel Tasting Weekend used to be a small weekend event, and now it's 60,000 people over two weekends."

In 2005, there were nearly 200 wineries in Sonoma County. Today, there are an estimated 550 wineries.

Some of the increase in the estimated economic impact was due to changes in the way the study was conducted, said Barbara Insel, president and CEO of Stonebridge Research Group in St. Helena. One change was the expanded definition of what types of businesses are part of the wine industry.

"It's not just growing grapes," Insel said. "We spent a lot of time tracking down the people making caps and barrels. We tried to pick up the suppliers last time, but it's like peeling an onion. You keep finding more and more people in the industry."

The numbers also were higher in part because the researchers gleaned more information about the number of grapes brought into Sonoma County to make wine. In 2005, winery executives weren't eager to discuss how many grapes they brought in from other counties. But this time they were more willing, she said. Crushing those grapes here means more jobs and impacts.

"There are as many grapes brought in to make wine as there are grown in Sonoma," Insel said.

In addition, a number of wine industry suppliers relocated from Napa to Sonoma because the county is more affordable, Insel said.

About $8 billion of the total economic impact came directly from wine-related businesses, while about $5 billion was based on secondary impacts like a winery employee buying lunch at a nearby deli, Insel said.

The report estimates the wine industry, directly and indirectly, provides 54,297 full-time equivalent jobs in Sonoma County and supports $3.2 billion in total wages, compared to 27,534 jobs and $1 billion in wages in 2005.

The state Employment Development Department estimates there were 182,000 wage and salary jobs in Sonoma County at the end of 2012.

"We just think it's important that the wine industry recognizes and understands the impact we have on the community, but also that the community as a whole recognizes how important the wine industry is in supporting the economy," Comfort said.

Wineries generated $3.05 billion in sales in 2012, up from $2.1 billion in 2005, according to the research.

According to the study, wine-related tourism in Sonoma County generated more than $1.25 billion in 2012, up from $263 million in 2005, an increase of 475 percent.

"That is a huge number, but that does mirror our numbers," said Tim Zahner, chief marketing officer at Sonoma County Tourism. "Trendwise, we do seem to be back to pre-recession levels for hotel occupancy."

Sonoma County Tourism was founded in 2005, and before that, there were fewer county-wide initiatives, Zahner said.

"It doesn't surprise me, because there's been an incredible amount of growth in that time," Zahner said.

Transit occupancy tax collections in the county, one measure of the impact of the tourism industry, stood at about $20 million in 2005, fluctuated with the recession, and reached about $24 million in 2012, according to an annual tourism report published by the county Economic Development Board.

The tourism impact in the Stonebridge report assumes the wine industry is responsible for about 60 percent of Sonoma County tourism, a conservative estimate, Insel said.

"Sonoma awareness is really significantly higher than it was in 2005, so you have more visitors," Insel said.