Urban Value Is Weighted Diversity, Not Density: A Theoretical and Empirical Case for A Shift In Paradigm

Calls for densification have grown pervasive in contemporary urban planning. In the Americas, Africa, Asia, Oceania, and Europe, planners and schools of architecture advocate for increasing the number of housing units, offices, or commercial spaces per hectare. While this type of ‘density advocacy’ has been widely advertised for, we demonstrate that it suffers from significant pitfalls. The present article lists systematic flaws, explaining them theoretically, and following up with empirical experiments. The problems all emerge from the same root, the underlying physical definition of ‘density’. In particular, density is a linear metric, in which individual components are added together, without accounting for the multiplicative effect of interplay between components. This type of metric reflects well how inexperienced investors think. They value individual urban components—housing units, offices, commercial spaces, for example—assigning expected revenues from each type of investment. While this linear logic is straightforward, it does not take into account the multiplicative effect of interplay between components. However, cities are complex systems where urban value emerges exactly due to interplay between components. Therefore, we must call for a shift in paradigm from additive, linear to multiplicative, nonlinear modeling. Rather than valuing individual urban components—housing units, offices, commercial spaces—we suggest that one must value the interplay between them. A city is more than the sum of its parts. The present article substantiates this argument both theoretically and empirically. It showcases that density metrics support problematic investment schemes that lead into business cycles and exacerbate processes such as gentrification and segregation, which have emerged as a global challenge. To provide a solution to this problem, we introduce weighted diversity, a nonlinear framework that describes urban life more accurately than density metrics and does not have the same shortcomings. Drawing on extensive data from Wellington (New Zealand), as well as several comparison examples, we show that our technical implementation of weighted diversity, which we call CHOAMs, can be used to better describe urban life and support more productive investment schemes. As part of our focus on interplay and multiplicative effects rather than mere addition of separated components, we also take urban mobility into account, which proves particularly worthwhile, showcasing how different mobility options in Wellington enhance and diminish urban value in nonlinear ways across the city. Overall, by shifting from density metrics to weighted diversity, planners and investors, as well as architects, will gain a better description of how their city works, which will support smarter project development and benefit everyone.