Casey Ross | The Boston Globe

Boston needs to build 53,000 housing units by 2030 to keep pace with rapid population growth that is already increasing prices and squeezing out low- and middle-income residents, according to a city report.

The report by Mayor Martin J. Walsh’s administration, previewed by city officials on Wednesday, calls for $21 billion in private and public construction that would increase Boston’s overall housing stock by 20 percent over the next two decades.

During that period, the city’s population is expected to jump by 15 percent, to 709,000 people, according to the report. That would be Boston’s highest level since the 1950s, when large numbers of people began to leave the city for surrounding suburbs.

Walsh wants to limit further real estate price inflation by creating 20,000 units for middle-income residents, largely built by private developers. His plan would loosen zoning restrictions and provide financial incentives to encourage construction of taller buildings in outlying neighborhoods. It would offer developers tax incentives and other assistance to help reach that goal.

He also wants to increase annual city funding for low-income housing by 65 percent, to $51 million, and require developers of downtown luxury complexes to pay more and build affordable units at other locations. Read more