The city of Seattle expects to generate about 2,100 new affordable housing or rent-restricted units after the city council approved an upzone proposal to allow taller buildings in downtown and South Lake Union.

The Incentive Zoning program allows developers to build taller, in exchange for building affordable housing units. They also have the option of paying a fee to the city for affordable housing if they opt not to build it themselves.

Incentive zoning has been an option since 2004. This new ordinance makes the choice mandatory.

Most developers currently choose to pay the affordable housing fee. The city says it's received $100 million from developers for affordable housing since 2004. $23.1 million was paid out in 2016 alone.

Figures from the Downtown Seattle Association show 959 affordable housing units have been built using those funds, in that time.

"This is an exciting win," said Don Blakeney, V.P. of Advocacy and Economic Development for the Downtown Seattle Association. "We are going to build more affordable housing. We are seeing more people feeling priced out and move to North Bend of Tacoma. And we want to keep people in Seattle."