Average asking rents and occupancy rates in Southern California's apartment market will continue to rise steadily this year, with average rent increases of 3.5% to almost 6%, according to a forecast to be released today. The average rental rate for a two-bedroom apartment should rise to about $1,500 in Los Angeles County, $1,520 in Orange County and $1,080 in the Inland Empire, according to data compiled for the Casden Real Estate Economics Forecast from USC's Lusk Center for Real Estate.