SAN DIEGO—The first quarter of the year marked the 11th straight quarter of positive rent office rent growth, with rents countywide increasing 5.3% year-over-year, according to a recent report from Jones Lang LaSalle's Southern California offices.

The supply of large blocks and high-end class A space continued their decline during the period, which is one of factors that is boosting rents, according to the firm's First Quarter San Diego Officer Report:

While there remains areas of value and opportunity in lower-demand submarkets, rents in these submarkets are also seeing robust growth. Kearny Mesa, while still a more affordable submarket, had the highest year-over-year rent growth at 8.9%.

Vacancy continued on its downward trajectory, dropping 120 basis points year-over-year. While net absorption was slightly negative this quarter, 2014 posted the highest net absorption since the recession, which contributed to the decrease in vacancy, JLL noted.

With the flight to quality, much of the activity has been among class A properties, which now have a direct vacancy rate in the single digits (9.4%) down from a high of over 20% during the recession. Class B assets have also experienced a drop in vacancy, though not as dramatic. The direct vacancy rate at end of the quarter closed at 15.4%.

Since year-end 2014, tenant demand in the I-15 corridor has increased by over 50%. There are nearly 730,000 square feet of active requirements from a range of industries including defense, healthcare, technology, engineering, and life sciences. With a relatively low total vacancy rate of 12.8%, the increased tenant demand will contribute to the tightening of this submarket.