Urbanization facilitates separation and it is good for everyone

From Human mobility networks reveal increased segregation in large cities by Hamed Nilforoshan, et al.  From the Abstract:

A long-standing expectation is that large, dense and cosmopolitan areas support socioeconomic mixing and exposure among diverse individuals1,2,3,4,5,6. Assessing this hypothesis has been difficult because previous measures of socioeconomic mixing have relied on static residential housing data rather than real-life exposures among people at work, in places of leisure and in home neighbourhoods7,8. Here we develop a measure of exposure segregation that captures the socioeconomic diversity of these everyday encounters. Using mobile phone mobility data to represent 1.6 billion real-world exposures among 9.6 million people in the United States, we measure exposure segregation across 382 metropolitan statistical areas (MSAs) and 2,829 counties. We find that exposure segregation is 67% higher in the ten largest MSAs than in small MSAs with fewer than 100,000 residents. This means that, contrary to expectations, residents of large cosmopolitan areas have less exposure to a socioeconomically diverse range of individuals. Second, we find that the increased socioeconomic segregation in large cities arises because they offer a greater choice of differentiated spaces targeted to specific socioeconomic groups. Third, we find that this segregation-increasing effect is countered when a city’s hubs (such as shopping centres) are positioned to bridge diverse neighbourhoods and therefore attract people of all socioeconomic statuses. Our findings challenge a long-standing conjecture in human geography and highlight how urban design can both prevent and facilitate encounters among diverse individuals.

Reading through the methodology, there are plenty of minor red flags, but nothing I could see as a major issue.  It is complex work being done in a novel fashion and needs replication but I suspect it will end up being reasonably robust.

Discussion of segregation in the US in urban environments is prone to error and manipulation.  Fifty and a hundred years ago there were de facto and de jure instances of government sanctioned racial segregation in major cities.  But de jure went away more than fifty years ago and de facto has become increasingly difficult to document.  

State sanctioned racial segregation is long gon  e.  Interestingly, it seems to me like the argument shifted 10-15 years ago from arguments that segregation was still occurring to arguments about how the residual impacts of past segregation were still being felt.  And always as a predicate to an argument for compensation.  So no longer a principled argument about data and reality and now mostly a grift.  

And regardless of past racial segregation, what has always been true in the past and remains true today is the prevalence of affiliative (not State sanctioned) class segregation.  Which is not a problem but a function of the First Amendment ("right of the people peaceably to assemble.")  People are entitled to live where they wish and with whom they wish and the affiliative nature of all human communities means that there is an affiliative nature to human residential patterns and interactions.

Rich affiliate with rich.  Educated with educated.  Profession with profession.  Religion with religion.  Language with language.  If people are allowed to choose where and with whom they will live, the most amazing (and unpredictable) patterns of residence will emerge based on the relative prioritizations of affiliative strength and urban context.

These patterns are rarely about keeping people out (illegal anyway) but about individual choices to affiliate with those with whom we each have the greatest affiliation.

And given that commonality of attributes is highly correlated with efficiency of communication and productivity, there are some interesting second-order effects.  If you live in an area of co-religionists in whom you have high trust because one's word is one's bond, and if you therefore can dispense with the cost of defensive contracts you might use in a more heterogeneous environment, all of a sudden, your affiliative choice of location is associated with a correlated rise in productivity.

The productivity of urban areas, in comparison with smaller cities and towns, is a long established phenomenon with multiple speculative causal reasons for the increased observed productivity.  My preferred explanation is increased specialization owing to density, in combination with affiliative associations allowing greater efficiency and effectiveness of communication and interaction.  

This research is consistent with those conclusions.  

We end up with two paradoxes that are integral with one another but ill understood.

Prosperity causes inequality.  The first is the well documented (but not well accepted) phenomenon that the strongest causal factor associated with individual economic inequality is economic prosperity.  The richer and more prosperous a country becomes, the more inequality there is.  But also the less poverty.  Absolute misery (poverty) is reduced to the extinction point but at the cost of rising relative misery (envy from economic inequality.)  There is no policy yet discovered which reduces inequality without also, and necessarily, reducing societal economic well-being.

Urbanization facilitates separation.  That is what is being suggested in this research.  The larger the city, the more opportunity there is for social and economic affiliative behavior (and specialization.)  The greater the group affiliation, the greater the prosperity.  Increased freedom of assembly leads to greater affiliation which leads to greater specialization which leads to greater group separation which leads to greater communal prosperity.

If you want everyone to be better off emotionally and economically quit focusing on theoretical problems that aren't real (income inequality and group affiliation) and instead focus on enabling people to make their own free choices.  Seems easy to do but it requires central planners to quit trying to impose their will on others.  And that is actually hard for them to do.