Small Bias – Big Effects

  

We associate the term bias with “bias against,” but not so often “bias towards,” or pro bias.  But in a famous simulation by economist Thomas Schelling, it is the pro bias, or general preference, that can finally create an outcome of de facto segregation of housing. People feel more comfortable in the company of people like themselves.  It is not so much a matter of what they look like as how they think. Shared values, which in this case means a mindset of assumptions - values collectively accepted as true - trumps everything else, regardless of other differences.   

Here is the way this pro bias operates to create housing choice—where people choose to live based on what group the neighbors belong to, as described by economist Tim Harford in The Logic of Life (2008). 

People are happy to live in mixed neighborhoods until they are outnumbered 2 to 1, or one-third of the area population, using a chessboard as a model of an integrated society of households. As white pieces get too many black neighbors (and vice-versa), a wave of segregation washes over the board.  Chess pieces surrounded by too many of the opposition move away, and doing so consolidates a picture of black homogeneity and white homogeneity (p.111). 

This process of a simple rule about preference for living in a place not too dominated by the “other side” was first modelled by Schelling, a game theorist who wondered what kind of social behavior could be explained by game theory: what happened when a single person moved to avoid being socially isolated (Schelling won the Noble Prize in 2005 by pursuing this question). 

“Schelling’s chessboard models showed that all it takes is a mild preference against being too heavily outnumbered…. Pessimists would point out that his model suggests that extreme segregation is almost inevitable” (Harford, p. 115).  Some claim that as little as a 10% incursion by a different group is enough to launch an avalanche of movers away (“white flight”) and thereby toward a more homogeneous settlement.  By following the outcome of game theory simulations, we can see that final outcomes can be unexpected, unintended, and perhaps even less than desired by any and all players. 

Stanford Encyclopedia of Philosophy opens its definition of Game Theory with this statement:

Game theory is the study of the ways in which interacting choices of economic agents produce outcomes with respect to the preferences (or utilities) of those agents, where the outcomes in question might have been intended by none of the agents (Sept. 3, 2023 ed.).

What appears to be an anti-bias against those different from ourselves can be seen, at the same time, not as an inbred prejudice against those unlike us but as a pro-bias preference for living among those whom we better relate to.  Flexing the reward system for “otherness” into some sort of affinity for those unlike ourselves can dull or nullify the expected social effects of housing location, if these rewards operate within the value bias of the group.  Class can overcome race, for example.

College towns and tourist destinations display a greater mix of ethnic types based on a common bond as middle-class.  And at the Disney parks, an enclave of highly mixed types and origins, race is rarely an issue because the park is recognized as a safe space.  Gay enclaves are known for both mixing and stabilizing what were once lower-end city districts, because gays generally do not need to prioritize good school districts in their housing agenda. Their social lives also generate more public safety by keeping streets and bistros busy well into the evening. 

Harford’s book offers several related examples of large effects from small biases.  Some depend on time of day and weather. For example, public playgrounds such as Hackney Downs in London experience social swings from moms and their children during the day to the young male teens who move in to dominate after twilight. This incursion switches the family-friendly sunlit atmosphere to edgy and unwelcoming.  The social theme instantly transforms from warm to cold with the teen “negative externality” transfer.  The openness of public space means that more negative behavior drives out the genteel and middle-class ethic--the ongoing problem with "public" parks.

In the same way, a city’s preference for tall building blocks exerts a bias toward street crime.  How?  By limiting the effect of “eyes on the street” that keeps crime rates down by citizen surveillance and intervention.  In areas with eyes at street level, safety increases as more pedestrians are attracted in.  The safety bias is self-sustaining and positively reinforcing.  Gay gentrification promotes such busy, safe, and engaging street dynamics in a “positive externality.”  This is one reason the middle class, whatever its politics, does not mind gay neighbors--especially homeowners