DOI: 10.3886/e237845v2
title: Intergenerational Kin Dispersion

description: This study examines intergenerational kin dispersion in the United States during the nineteenth century using genealogical data from population-scale family trees. Families are traced across three generations: grandparents (G1), parents (G2), and grandchildren (G3). The analysis is based on G1 couples born between 1785 and 1866, with descendants extending to G3 born through 1906. To ensure consistent geographic coverage, the data are restricted to lineages in which both G1 partners, their children, and grandchildren were U.S.-born.
From these genealogical records, three-generation birthplace sequences were constructed and used to calculate aggregate kin dispersion metrics: Stayer Symmetry (ISI-S), Migrant Symmetry (ISI-M), and the Intergenerational Symmetry Index (ISI). These indices measure whether families remained in or moved away from ancestral states, balancing attraction, retention, and dispersion across cohorts. Historical state boundaries from NHGIS were integrated to align genealogical records with the geographic context of the time.
This shared repository provides both birthplace sequence data and pre-calculated kin dispersion metrics, enabling other researchers to reuse and extend the dataset for a wide range of projects. The data can support studies of migration, settlement, kinship networks, demographic change, and spatial processes in U.S. history, as well as provide a foundation for comparative analyses and methodological development in historical demography and spatial social science.
description: We examine kin dispersion across three generations: Generation 1 (grandparents), Generation 2 (parents), and Generation 3 (grandchildren), recorded in U.S. genealogical family trees. G1 consists of couples with birth years in ten-year cohorts from 1785–1796 through 1855–1866, restricted to cases where at least one of the G1 couple was U.S.-born. After applying the additional constraints described below, however, our final samples include only G1 couples in which both partners were born in the U.S. G2 serves as the focal generation, linking upward to G1 and downward to G3 (grandchildren born through 1906). To ensure consistent U.S. coverage and data quality, we include only families where G1 couples have at least two G2 children with complete birth year and birthplace, and where at least two of those G2 children each have at least two G3 offspring with complete information. Additional filters address improbable birth spacing and long sibling spans. . Smallest Geographic Unit: State
description: The dataset is derived from large-scale genealogical family trees assembled from publicly available historical sources (Koylu et al., 2021). We process these records into three-generation birthplace sequences, applying filters to address common inconsistencies in crowdsourced genealogies (e.g., improbable sibling birth gaps, overlapping generations, and missing birthplace information). Historical state boundaries from the National Historical Geographic Information System (NHGIS) are integrated to standardize geographic references over time. To ensure comparability, families are restricted to those with at least one U.S.-born grandparent (G1) and complete birthplace information for parents (G2) and grandchildren (G3). Aggregate kin dispersion metrics (Stayer Symmetry, Migrant Symmetry, and Intergenerational Symmetry Index) are calculated at cohort and state levels using SQL and Python pipelines. <br><br>The dataset is released in two complementary parts. The cohorts_migration_sequence files contain the complete three-generation birthplace sequences for each G1 cohort, including weighted counts for all four paternal and maternal lineal paths. These tables provide the raw lineage-specific transition patterns from which all symmetry metrics are derived. The dispersion_symmetry files then summarize these transitions into stayer and migrant symmetry measures for each cohort and path, offering an interpretable, state-level representation of how birthplace continuity or dispersion varies across generations. Together, the two sets of files give users access both to the underlying migration sequences and to the derived metrics used in the analysis.<br><br>dispersion_symmetry.zip file contains migration and symmetry metrics for each cohort and lineal path. Each CSV file contains symmetry outcomes for a single G2 cohort and a single lineal path, with separate files for stayers and migrants. The rows represent state-level measurements derived from directed parent–child transitions within the specified path (e.g., G1 father → G2 mother). The column g2bplace has been translated from RootsWeb state identifiers into census state codes using a lookup table to ensure spatial compatibility across datasets. For each cohort–path–metric combination, the table reports weighted counts and the resulting symmetry value quantifying directional agreement between ancestral and descendant birthplaces.<br><br>cohorts_migration_sequence.zip file includes migration sequences for each cohort. One CSV file per G1 birth cohort (e.g., cohort_1785_1796.csv). Each file lists all three-generation birthplace sequences in the form: <br><br>g1bplace, g2bplace, g3bplace <br><br>where each birthplace is a standardized U.S. census state code for the G1 grandparent, G2 parent, and G3 child.
The dataset also provides four weighted count columns, one for each possible lineal path from G1 → G2 → G3:


g1fg2f — grandfather → father → child


g1mg2f — grandmother → father → child


g1fg2m — grandfather → mother → child


g1mg2m — grandmother → mother → child


Each column gives the normalized contribution (weight) of all families that exhibit that specific three-generation birthplace sequence along the corresponding path. Rows with zeros in a given column indicate that the sequence does not occur along that path.
These tables offer a compact summary of all intergenerational birthplace transitions for each cohort, separated by paternal and maternal lineage.<br>