Measuring and mapping long-term changes in migration flows using population-scale family tree data

ABSTRACT

Studying migration over a long period is challenging due to lack of data, uneven data quality, and the methodological challenges that arise when analyzing migration over large geographic areas and long time spans with constantly changing political boundaries. Crowd-sourced family tree data are an untapped source of volunteered geographic information generated by millions of users. These trees contain information on individuals such as birth and death places and years, and kinship ties, and have the potential to support analysis of population dynamics and migration over many generations and far into the past. In this article, we introduce a methodology to measure and map long-term changes in migration flows using a population-scale family-tree data set. Our methodology includes many steps such as extracting migration events, temporal periodization, gravity normalization, and producing time-series flow maps. We study internal migration in the continental United States between 1789 and 1924 using birthplaces and birthyears of children from a cleaned, geocoded, and connected set of family trees from Rootsweb.com. To the best of our knowledge, the results are the first migration flow maps that show how the internal migration flows within the U.S. changed over such a long period of time (i.e. 135 years).

KEYWORDS:

• Migration
• family trees
• flow mapping
• user-generated big data
• U.S. migration history

Acknowledgments

We would like to thank the anonymous reviewers whose comments and suggestions improved this manuscript and our research significantly. We also would like to thank David Hacker for helping us identify the historical and transportation periods in the United States history so that we could compare these periods to the data-driven temporal periods.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data and codes availability statement

The family tree data used in this study were derived from the following resources available in the public domain: https://home.rootsweb.com between the dates of February and August 2015. Based on the effective date of the Revised Terms and Conditions of Ancestry.com by 25 July 2019, we are not able to share the original GEDCOM files published on rootsweb.com. We share the anonymous birth events and locations as a database backup file (at state and territory level) that can be used for extracting the child-ladder migration. We share (1) the entire source code for our methodology; and (2) database backup file and the medium and final data products at the following data source link: https://doi.org/10.6084/m9.figshare.14602677.v4.

Supplementry material

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by the Institute of Museum and Library Services [LG-00-14-0030-14].