SAN FRANCISCO -- On the steps of San Francisco City Hall Friday, state Sen. Carole Migden, Supervisor Chris Daly and affordable housing organization representatives announced the introduction of a bill that would help regulate the number of rent-controlled housing units in California.

"Rent control remains the largest and most effective affordable housing program," Daly said during a news conference.

Senate Bill 1299 would allow city or county governments to require housing developers to create as many rent-controlled units as are demolished. As it is now, property owners can evict tenants without a stated reason to demolish a building and are not required to supply new rental units.

"We do not want to become just a billionaires' abode," Migden, D-San Francisco, said.

San Francisco has lost about 2,400 rental units in the last 10 years, according to Migden. In that same time, Los Angeles lost more than 11,000 units. Those hit hardest by the lack of affordable housing are the state's most vulnerable populations, including young people and people of color.

"We don't want seniors kicked out," Migden said. "We don't want people with HIV kicked to the street."

San Francisco Tenants Union Executive Director Ted Gullicksen said Parkmerced - the biggest complex in the U.S. west of the Mississippi River - could be the next site affected by demolition due to San Francisco State University development.