Orange County asking rents were $1,885 a month in the first quarter, up $73 a month or 3.8 percent year over year. In the Inland Empire, apartment rents averaged $1,319 a month, up $42 monthly or 3.0 percent from the first quarter of 2017.

Vacancies in the region, meanwhile, ranged from 3.2 percent in the Inland Empire to 3.4 percent in L.A. County and 3.8 percent in Orange County, according to Reis. Vacancy rates have been under 5 percent for the past six years, a major factor in why rents have gone up steadily since late 2010.