Chicago-based Golub & Co. and Los Angeles-based co-developer CIM Group have broken ground on a 41-story, 397-unit apartment tower in Chicago's South Loop, fueling a boom some analysts predict could add nearly 9,000 residences to downtown Chicago by year-end 2016.

Earlier this year, CIM broke ground on a 34-story, 690-unit apartment tower atop a four-story mall in Chicago's Loop, the largest such project to rise in the district in years.

Both projects join new fewer than 17 residential developments under construction in downtown Chicago, including a 402-unit tower undertaken by Chicago-based developer John Buck Co. and a 498-unit project by Optima Inc., a Glencoe, Ill.-based developer.

Similar booms are under way in most major Midwest markets, particularly in central business districts, a trend analysts partially attribute to a desire by Millennials to postpone home ownership in favor of renting in areas in closer proximity to public transportation, retail, restaurants and places of employment.

Minneapolis/St. Paul, with a combined population of only 700,000, added 6,600 units this year and 4,000 units in 2013. The $400 million Downtown East, a mixed-use development currently under construction, will add an additional 193 units to Minneapolis, where as many as 10 residential towers are expected to break ground next year.

Despite concerns about gluts, demand is maintaining pace with supply as new developments come on line. In Chicago, developers are leveraging demand for units in emerging markets, such as Chicago's West and South Loop.

“CIM identified Chicago’s South Loop as a CIM Group Qualified Community as it possesses the attributes that fit its longstanding investment model, one that focuses on urban districts positioned for economic expansion with solid infrastructure and transportation networks,“ CIM founder and principal  Avi Shemesh indicated in a statement.