The San Diego Regional Chamber of Commerce’s measure of business confidence fell to its lowest point since the survey began in 2013, following three months of year-long lows as businesses reported low expectations for future revenue growth.

The chamber’s Business Outlook Index from 21.3 in September to 17 in October. The index has historically averaged about 26, but has been steadily falling since June.

While roughly half of businesses in September predicted their revenues and industry conditions would improve, only about 40 percent of businesses in October felt the same way. One-person firms in particular experienced a heavy drop-off in optimism, falling to five from 19 over the past three months.

The one bright spot, according to index sponsor Silvergate Bank, were retailers, who predicted stronger revenues due to the impending holiday season.

“It’s great to hear that the retail sector is looking for a robust holiday season, which could have an overall positive impact on the outlook later on this year,” said Silvergate Chief Banking Officer Dino D’Auria said.