Mapping Mobility

By Reid Ewing

Upward mobility weighed down by sprawl

Upward mobility. This American ideal is rooted in the Declaration of Independence: Hard work is enough to create upward mobility, with greater opportunities, personal security, and affluence. But is the American ideal equally achievable by all societal groups?

Recent studies show that the U.S., as the land of opportunity for all, has one of the lowest rates of upward mobility in the developed world. Only a few citizens leave the class into which they are born for a higher one. Downward mobility also is just as common as upward mobility, particularly for African Americans, but also for the middle class in general. In the U.S., a person born in the lowest economic class has only about a two percent chance of ending life anywhere near the top.

Upward mobility is an often-researched topic, with scholarly articles on the subject dating back to the 1950s and 1960s. Much of the research has focused on race, family background, income, and family structure, particularly divorce, as determinants of upward mobility. Poorly staffed and funded schools in poor and working-class neighborhoods, inadequate prenatal nutrition and health care, and environmental hazards are some of the factors that affect the success of a poor young person seeking a better life.

Equality of opportunity

A study of upward mobility by a team from Harvard and UC–Berkeley made the news recently. Their study is appropriately titled "The Equality of Opportunity Project." Among the findings of interest to planners: ". . . intergenerational mobility varies substantially across areas within the U.S. For example, the probability that a child reaches the top quintile of the national income distribution starting from a family in the bottom quintile is 4.4% in Charlotte but 12.9% in San Jose."

What struck me immediately about this and similar statements is a possible connection to sprawl. In the metropolitan rankings created by my team at the University of Utah (http://gis.cancer.gov/tools/urban-sprawl), Charlotte is at the sprawling end of the scale, while San Jose is far more compact. Metropolitan sprawl — and poor accessibility, a key sprawl indicator — may contribute to the low rates of upward mobility for lower income classes in sprawling metropolitan areas. Considering the fact that those with low incomes have limited transportation mobility, inaccessibility of job opportunities could affect their ability to get ahead. Other causal pathways may also exist between sprawl and upward mobility.

The Harvard team tested for correlations between upward mobility and possible causal factors (computing simple correlations). They found strong correlations between upward mobility and six factors: income growth, racial segregation, income inequality, quality of K–12 schools, social capital, and family structure.

They speculated about a possible link between sprawl and upward mobility, but used a yardstick that doesn't quite work: ". . . we also find that upward mobility is higher in cities with less sprawl, as measured by commute times to work." There are much better ways to measure sprawl than commute times to work. Indeed, some of the most compact metropolitan areas have the longest commute times, by virtue of their size and heavy use of transit (which typically involves longer travel times than automobiles). Think New York City and San Francisco.

Sprawl and getting ahead

To see how sprawl affects upward mobility, our University of Utah team estimated a structural equation model. We used data on upward mobility and causal variables from the Equality of Opportunity database but added a "sprawl" index whose values are high for compact metro areas, and low for sprawling areas. The measure of upward mobility we chose was the probability that a child born to a family in the bottom quintile of the national income distribution reached the top quintile of the national income distribution by age 30.

Relationships are mostly significant and as expected. As our index doubles (compactness increases by 100 percent), the probability that a child born to a family in the bottom quintile of the national income distribution will reach the top quintile by age 30 increases by about 41 percent. For the average poor kid in our sample, with an eight percent chance of moving up into the top quintile, this represents an increase of 3.2 percent in absolute terms, well within the range of upward mobility differences from metropolitan area to metropolitan area.

The importance of upward mobility for the poorest of the poor is something that everyone from the pope to the president can agree on. It is nice to think that planners may contribute to such a worthy goal by simply containing sprawl.

Reid Ewing is a professor of city and metropolitan planning at the University of Utah and an associate editor of the Journal of the American Planning Association. More than 40 past columns are available at mrc.cap.utah.edu/publications/research-you-can-use. The Equality of Opportunity report is downloadable at http://equality-of-opportunity.org/images/mobility_geo.pdf.