Beginning in the 1990s, and accelerating since, US cities are being reborn.  Cities are “cool” again, attracting a spirited population of urban enthusiasts, including empty nesters returning from the suburbs, and Generation X’ers—young college graduates, singles and largely childless couples. The combination is what Richard Florida has branded the “Creative Class”—those whose ideas and income is needed to revitalize cities.  It is also feeding a “New Urbanism”—for some, “livable, walkable, bikable cities,” and for others a more narrow, even elitist, impractical and inequitable view.  Whatever side of the debate one appropriates, new urbanists are partly responsible for reenergizing in-town neighborhoods and commercial downtowns that have lain fallow in the hours after the normal work day. 

For different reasons the two demographic tails, Gen X’ers (singles, couples, LGBTs) and higher income empty nesters, are driving up housing prices, incentivizing housing configurations that may not support families over the long run, and creating a new tableau of amenities (e.g., eating and entertainment), which often exclude others in the population mix, and create a less diverse social fabric in the end.  Urban revitalization is occurring alongside re-concentration of poverty—in cities and the greater metropolis, posing separate concerns for its effects on the poor and its future impact on urban revitalization.

The response to income polarization in the wake of revitalization has been a variety of techniques to create diversity (e.g., clawing back some below market units as a condition for concessions on density limits in new projects, adding requirements for public recreational or open space in new developments in order to serve a broader mix of users, new tax relief for limited income groups).  Mixed income developments (e.g., HOPE VI and its successors), in part because of their complexity and long implementation time, inevitably include few original residents and fewer affordable units.  In the current revitalization environment sound low income housing may be destroyed in the name of revitalization but in the process create a new diaspora of low income families and loss of diversity that was the objective of mixed income approaches.

Understanding the utility of demographic diversity in urban rebirth is both a definitional and conceptual problem.  How we define middle class (e.g., spatial boundaries for AMI calculations) is central to considering targets for affordable housing, public school enrollment, planning and pricing amenities, and fiscal strategies including taxing and spending of public funds. Conceptually, we have not agreed upon the value of diversity, including long term social and fiscal implications of income diversity, in order to reestablish it as an a priori objective for urban revitalization. Loss of income diversity presents particular challenges to rapid urbanization in countries such as China, including choices for integrating new in-migration into urban profiles and the potential for deep social divides.  The paper will review recent analysis of creation or loss of urban diversity and program approaches to address it, and develop a conceptual framework for understanding the importance of integrating diversity into urban development policies in the US and elsewhere.