The apartment vacancy rate in San Diego County fell to 2.3 percent this fall, nearly halving the 4.1 percent vacancy rate from one year earlier, according to the San Diego County Apartment Association’s semi-annual survey of landlords.

The group said the increased demand for rentals mirrors a national trend driven by the mortgage crisis that displaced thousands of homeowners because of their inability to make monthly payments. The increase was also a result of an economic recovery and job growth, meaning more people are living on their own, SCCAA said.

The survey sent to nearly 6,000 property owners and managers found the average monthly rent for all unit types to be $1,321. The average rent on studios was $812; for 1-bedroom units, $1,066; for 2-bedroom units, $1,463; and for 3 or more units, $1,813.

One year ago, the average rent for all units was $1,311.

Some relief in the form of increased apartment development is on the way. Multifamily permits made up 63 percent of the 4,079 building permits issued through July in the county, according to the Building Industry Association of San Diego County.