Overview

Over 14 million Americans migrate from one place to another in an average year. Collectively, these migrants represent a powerful economic force, influencing conditions not only in the places they left behind but also in those to which they moved. Individuals–for the most part–migrate to take advantage of better economic opportunities, or to live in environments they consider to be more pleasant.

Researchers study migration patterns for three primary reasons. First, they want to document changes in population in an area that are due to migration. The ability to forecast the number of residents in a community over a five- to ten-year horizon is critical for planners, for example. Second, migration researchers want to understand why individuals and their families migrate. In other words, what are the triggers that cause people to move, and are there discernible characteristics that make some people more likely than others to move? Third, migration researchers want to quantify the impact of migration on local economic conditions and human welfare. Businessmen and businesswomen and elected state and local officials have much at stake when people migrate, as discussed in Section I of this text.

This chapter on population migration and local labor markets consists of five sections. The first four sections deal specifically with migration topics, while the fifth examines local labor markets, which are in some ways more related to commuting than to migration patterns. Each section is self-contained, and readers are invited to skip directly to the section of primary interest. Section I is written for the general reader and has no pre-requisites. Sections II and III contain material appropriate for senior-level or beginning undergraduate-level classes, including some relatively advanced econometric models in Section III. For the most part, these sections can be skipped without loss of continuity. Sections IV and V briefly use matrix algebra but are otherwise accessible to readers without a background in linear algebra. Exercises and discussion questions are included for each of the sections.

Section I presents a general introduction to the topic of migration and reviews contemporary migration patterns and issues. This includes a discussion of why migration is important to both the public and the private sectors, as well as a review of past major migration trends between rural and urban areas. These trends have had profound impacts both on areas losing migrants and on areas receiving migrants. For the latter areas, the impact has often been negative–i.e., in the form of additional congestion. Other topics discussed here include urban and suburban migration, barriers to migration, occupational mobility, return migration, retirement migration–an increasingly powerful demographic force–as well as U.S. migration policy. The topics of occupational mobility and barriers to migration are especially significant in the current era of welfare reform, with its emphasis on employment for former welfare recipients. Return migration occurs when people return to the place where they were born. Section I concludes with a discussion of migration patterns of foreign immigrants and a brief review of migration issues in foreign countries.

Section II presents the theory of population migration in detail. This section traces the historical development of migration theory, starting with a writer in the nineteenth century whose early insights into migration behavior proved to be remarkably robust to challenges from subsequent scholars. The gravity model of population migration is discussed at length since it continues to be the basic platform for much of the work on migration. From the gravity model the discussion moves to models of in-migration and out-migration, with their greater emphasis on the conditions that exist in both the migration destination and origin. This is followed by place-to-place migration models. In recent years, considerable attention has been devoted in migration studies to understanding the role of compensating wage differentials between locations. This topic is reviewed in Section II, which concludes with a brief presentation of migration dynamics. Links are provided in this section to Section III, which contains applications of the theoretical models.

In Section III applied migration studies are reviewed. Considerable discussion is devoted to the characteristics of migrants as well as the economic and physical features of the places to which they migrate. This is followed by a review of selected econometric studies of migration, which examine the independent effects of various explanatory variables. In some cases, such as educational attainment, mixed results are obtained from the regression models. In other cases, such as age, there is a clear negative relationship between aging of the migrant and the propensity to move. A large applied literature exists in the area of migration which uses limited dependent variables estimation methods. Among these are neighborhood and community choice models, as well as the mover-stayer model.

Section IV addresses practical issues that arise in migration studies as well as methodological concerns or questions. Issues discussed include the time period over which migration is measured, the appropriate spatial unit to be used and what difference that unit makes. Various methods of estimating migration flows are presented, including Markov transition matrices, and migration efficiency measures are developed. These measures are subsequently applied to migration data for the 50 states of the United States. Migration forecasting is critically important for planners, and various forecasting methods are presented in this section. The concluding section reviews sources of migration data and provides Internet addresses for selected migration-related sites.

Some authors define migration as a move between two different spatial labor markets. Local labor markets are the subject of Section V. Both conceptual and empirical issues are reviewed in this section. Key variables that distinguish different local labor markets are discussed, such as unemployment rates and wages. Practical issues that arise in defining local labor markets are examined at some length, and procedures that have been used in the literature to delineate local labor markets–such as cluster analysis–are presented. Recently there has been some interest in testing for the amount of spatial association that exists within local markets, including labor markets, and the results of one of these studies are presented briefly. The section concludes with a brief discussion of the spatial mismatch hypothesis as it relates to local labor markets and worker mobility, and current federal economic development strategies targeted at local labor markets in general.