The vacancy rate among San Diego apartments plunged to 2.8 percent, a level not seen in a decade, according to a report from the San Diego County Apartment Association.

The rate is down from 4.5 percent one year ago, the Apartment Association said.

The last time the vacancy rate was this low was 2002, when it was 2.5 percent, Apartment Association Executive Director Alan Pentico said.

“The demand for rental housing just keeps getting stronger,” he said.

Meanwhile, the association has seen a surge in rental property ownership as more people throughout the region invest in single-family homes rented as one or two units. The trade group has also seen an increase in the number of permits and construction of apartments, but the demand is still outstripping supply.

The latest apartment survey found the lowest vacancy rate in San Diego at 2.7 percent, while the highest rate was in the South Bay where it was 2.9 percent.

The average rent for all apartments in the county was $1,260, which was down 5 percent from a year earlier, the Apartment Association said. Nevertheless, the average for some of San Diego’s more desirable areas will be considerably higher.