The Decline in Mobility and its Impact on Passenger Travel

Project Number


Project Summary

People in the United States (US) are among the most mobile in the world (Malloy et al, 2011).   Annual migration rates were close to 20 percent from 1947-1983 (Frey, 2009); however, this rate has steadily fallen reaching a low of 13 percent in recent years. Some data (Frey, 2009; Painter and Yu, 2014) suggested that this rate has fallen even further in the recession, but Kaplan and Schulhofer-Wohl (2012) suggest that rates have not declined further after accounting properly for data imputations. Regardless of the debate surrounding the most recent changes, understanding the determinants, magnitudes, and characteristics of the decline in inter- and intra-urban mobility is important for urban transportation planning and policy. The current study explores factors that explain the decline, empirically analyzes effects of the decline on metropolitan travel, and discusses broad implications for future transportation planning and decision-making. If geographical stability of populations is primarily driven by factors unrelated to their references/affinities for particular urban built and transportation environments, planners can more confidently attempt at influencing travel behaviors and patterns using integrated land use-transportation-pricing tools. The stability also simplifies demand analyses/assessments and facilitates targeted investment decisions that potentially carry fewer risks than in the past.   This research addresses critical gaps in past research, and contributes to planning scholarship and  practice in multiple ways. Much of recent work on understanding the decline in mobility has simply  focused on documenting the decline (Frey, 2009; Malloy et al, 2011). Long-term declines have been observed across the entire age distribution with similar patterns occurring in most metropolitan areas in the US. There is less research understanding about why declines have occurred. Among the few papers, Kaplan and Schulhofer-Wohl (2013) claim that a reduction in the geographic specificity of returns to skills and an increase in worker’s information about the benefits of moving to other places can partially explain the decline. Some (e.g. Malloy et al, 2013) have speculated that the differences in consumption amenities across place may also explain some of the decline. This research will focus on understanding whether the changing demographic composition of the U.S. is related to the decline in mobility. While there has been an increase in the immigrant populations over the past 4 decades, this population is now much more mature and has been in the U.S. longer than it was in the 1980s (Painter and Yu, 2014). This could mean that there has been a decline in the mobility within the immigrant population simply due to this maturity. Further, we don’t know how the mobility of the second generation compares to the first generation.   To understand how these shifts in the population are impacting inter-urban and intra-urban mobility, this project will use Current Population Survey, American Community Survey, and other  transportation datasets (traffic flows, travel surveys, etc.) to decompose the decline in mobility by age, nativity, and across immigrant generations to understand the contributors to mobility over time. The analysis will include controls for labor market changes that the recent literature has used, and will focus on the Los Angeles region.   Passenger travel impacts will be analyzed using a three-part empirical study, focusing on the Los  Angeles metropolitan region. First, we will analyze how long-term population mobility [or stability] has, in part, affected highway/freeway traffic flow patterns across [sub]regions and along specific high demand corridors. Second, we will analyze how long-term demographic shifts across sub-regions has altered passenger travel behaviors across the sub-regions, and try to isolate the effect of mobility. Finally, we will use findings from the research to provide practical insights to planners, system managers, and researchers.

Project Status


Project Brief



Topic Area

Integrated Freight and Passenger Systems

P.I. Name & Address

Director, Graduate Programs in Public Policy; Director of Research, Lusk Center for Real Estate, USC Price School of Public Policy
University of Southern California
650 Childs Way
Ralph and Goldy Lewis Hall (RGL) 214
Los Angeles, CA 90089-0626
United States

Funding Source


Total Project Cost


Agency ID or Contract Number

Grant No: 65A0533

Start and End Dates

8/15/2015 to 8/14/2016