Urban Institute estimates suggest that millennials  - adults roughly 20-34 years old -  will form 15 to 18 million new households between 2010 and 2020. Compared with Baby Boomers, a greater proportion of those new householders will remain in big cities, having settled there for the first time as independent adults in their early 20s. Read Rolf Pendall’s article in The Atlantic Cities to understand the causes and implications of this demographic shift.