The news is out: San Antonio is the most income-segregated large city in the U.S. Pew Research published their data in August 2012 but we just read about it in an article by Richard Florida in Atlantic Cities.
When Jesus was asked by a lawyer “who is my neighbor?” he told the story of the Good Samaritan. His point was clear: your neighbor isn’t the guy who lives next door or even a member of your “tribe.” Your neighbor is the person who sees your need and helps. Your neighbor is the one who shows compassion.
It’s a lot easier, though, to be a good neighbor when your paths cross. You won’t stop and help the woman lying beaten and bloody by the side of the road if you don’t travel the same roads. She’s invisible to you. This is why residential income segregation matters.
The statisticians at Pew studied census tracts. (If you’d like to see data for your census tract, it is available here; make sure to change the year of the search to 2012, as the default year, 2014, is not yet functional.) Pew derived an indicator that they call the RISI: residential income segregation index. It is computed by adding the percentage of poor people who live in census tracts predominately populated by other poor people (defined as below 67% of the area’s median income, or $32,999 in San Antonio) and the percentage of rich people who live with mostly other rich people (defined as with incomes above 200% of the area’s median income, or $98,000 in San Antonio.)
In the Southwest, the 2010 RISI average was 57; the 1980 RISI average: 35. San Antonio San Antonio’s 2010 RISI score was 63 (the highest in the nation); in 1980 it was 39. In comparison: Houston (61/32), Dallas (60/39), Denver (55/34) and Phoenix (48/33).
Pew speculates about why the number is so high in San Antonio and other similar cities in the southwest:
For example, Houston, Dallas, San Antonio, Phoenix and Miami have all been among the nation’s fastest-growing large metropolitan areas during the past three decades—a growth that has been fueled in part by an influx of low-skill, low-wage immigrants from south of the border and in part by an influx of high-skill, high-wage workers and well-to-do retirees. These dual migration streams could well have contributed to a rise in residential segregation by income.
Our friend Mike Greenberg suggested that equally compelling explanations are zoning regulations and the practice of developers building homogeneous communities. Whatever the reason, it’s an important area to explore.
Here is some of the data so you can look at it yourself: 
