Papers
Research papers and publications.
Exploring Space‐Time Interactions in Fatal Opioid Overdoses
Sergio J Rey, Elijah Knaap, Alejandra Cabral, Jennifer Syvertsen
2025
This study investigates fatal opioid overdoses in Riverside County, California, between January 2020 and March 2023, employing advanced spatial‐temporal analysis methods to uncover significant clusters and their underlying contexts. By integrating global and local Knox tests, the research identifies …
The emergence of fentanyl in a stimulant landscape: Un/intentional use, social relations, and developing communities of care
Jennifer Syvertsen, Alejandra Cabral, Elijah Knaap, Sergio Rey, Robin A. Pollini
2025
Background: The introduction of fentanyl into the unregulated drug supply has drastically altered drug landscapes across the United States and increasingly contributed to overdose. As part of a larger study about opioid overdose, we assessed how the emergence of fentanyl has shaped health outcomes …
Unraveling Incommensurate Spatial Partitions: A Bipartite Graph Approach to School-Neighborhood Interactions and Their Impacts
Sergio Rey, Elijah Knaap, Zachary P. Neal, and Clio Andris
2024
This paper investigates the challenges and opportunities arising from incommensurate spatial partitions (ISPs) in regional science and spatial econometrics, focusing on how processes with overlapping yet distinct boundaries, interact and influence each other. ISPs are prevalent in various domains, …
Measuring Spatial Congruence in the School-Neighborhood Nexus
Sergio Rey, Elijah Knaap, Ran Wei, and Dylan Skrah
2024
This research addresses the critical need for a comprehensive understanding of the spatial dynamics between public schools and residential neighborhoods, both of which significantly influence children’s life outcomes. The study introduces innovative methodologies for examining the spatial …
The Geospatial Neighborhood Analysis Package: Open Tools for Urban, Regional, and Neighborhood Science
Elijah Knaap & Sergio Rey
2024
Understanding neighborhood context is critical for social science research, public policy analysis, and urban planning. The social meaning, formal definition, and formal operationalization of “neighborhood” depends on the study or application, however, so neighborhood analysis and modeling requires …
Measuring the Purple Line's Effect on Residential Rents: Spatial Econometrics and Causal Inference in Urban Policy Analysis
Elijah Knaap
2024
In this paper, I leverage a unique dataset containing unit-level observations on rental prices for units in Montgomery County, Maryland to build a series of hedonic models using a spatial econometric panel framework. Over the dataset’s time horizon (2015-2018), The Purple Line, a new light rail was …
Measuring Two Decades of Urban Spatial Structure: The Evolution of Agglomeration Economies in American Metros
Elijah Knaap & Sergio Rey
2024
In this paper we examine the evolution of urban spatial structure in U.S. metropolitan areas over nearly two decades. Using annual block-level data from the Longitudinal Employment Household Dynamics database, we introduce a technique for identifying regional employment centers that both adheres to …
Segregated by Design? Street Network Topology and the Measurement of Urban Segregation
Elijah Knaap, Sergio Rey
2023
Racial residential segregation is a longstanding topic of focus across the disciplines of urban social science. Classically, segregation indices are calculated based on areal groupings (e.g. counties or census tracts), with more recent research exploring ways that spatial relationships can enter the …
Reducing Racial Segregation of Public School Districts
Wei, Ran, Feng, Xin, Rey, Sergio, Knaap, Elijah
2023
Racial segregation in public education has been declared as unconstitutional for over 60 years in the United States. Yet many public school districts remain largely separate and unequal. A commonly used approach to reduce school segregation is redelineating school attendance zones to create more …
American Community Survey (ACS) Data Uncertainty and the Analysis of Segregation Dynamics
Wei, Ran, Knaap, Elijah, Rey, Sergio
2023
American Community Survey (ACS) data have become the workhorse for the empirical analysis of segregation in the U.S.A. during the past decade. The increased frequency the ACS offers over the 10-year Census, which is the main reason for its popularity, comes with an increased level of uncertainty in …
The Spatial Analysis of Gentrification: Formalizing Geography in Models of a Multidimensional Urban Process
Knaap, Elijah
2022
This chapter examines predominant and emerging approaches for conducting spatial analyses of gentrification; It begins with a brief review of relevant theoretical literature to describe why spatial analyses require formalizing gentrification studies in ways that unavoidably simplify a complex …
The Legacy of Redlining: A Spatial Dynamics Perspective
Rey, Sergio, Knaap, Elijah
2022
This paper investigates the long-term impacts of the federal Home Owners’ Loan Corporation (HOLC) mortgage risk assessment maps on the spatial dynamics of recent income and racial distributions in California metropolitan areas over the 1990-2010 period. We combine historical HOLC boundaries with …
The PySAL Ecosystem: Philosophy and Implementation
Rey, Sergio J., Anselin, Luc, Amaral, Pedro, Arribas-Bel, Dani, Cortes, Renan Xavier, Gaboardi, James David, Kang, Wei, Knaap, Elijah, Li, Ziqi, Lumnitz, Stefanie, Oshan, Taylor M., Shao, Hu, Wolf, Levi John
2021
PySAL is a library for geocomputation and spatial/geographic data science. Written in Python, the library has a long history of supporting novel science and broadening methodological impacts far afield of academic work. Recently, many new techniques,methods of analyses, and development modes have …
The Daily Ballet of Temporary Integration: Spatio-Temporal Segregation Dynamics in Metropolitan U.S.A.
Elijah Knaap, Sergio Rey, Renan Xavier Cortes, Wei Kang
2021
"A recent wave of scholarship examines the ways that daily activity spaces contribute to the experience of racial and ethnic segregation in large cities. In this paper, we take a different approach, leveraging administrative data on the residential and workplace locations of employees in large …
Smart Growth’s Misbegotten Legacy: Gentrification
Finio, Nicholas, Knaap, Elijah
2021
From the 1960s through the 1990s empirical literature established that the process of gentrification, the in-movement of higher-class individuals into disinvested urban areas, was occurring in cities across America. This phenomenon occurred despite population decline in major cities and the physical …
Changes in the Economic Status of Neighbourhoods in US Metropolitan Areas from 1980 to 2010: Stability, Growth and Polarisation
Kang, Wei, Knaap, Elijah, Rey, Sergio
2021
In this paper we move away from a static view of neighbourhood inequality and investigate the dynamics of neighbourhood economic status, which ties together spatial income inequality at different moments in time. Using census data from three decades (1980–2010) in 294 metropolitan statistical areas, …
Capturing the Relationship Between Spatial Structure and Individual Outcomes: Variation in the Concept of 'Access to Parks' and its Association with BMI
Elijah Knaap, Chandra A. Reynolds, Sergio Rey, Robin P. Corley, Sally J. Wadsworth
2021
"In this study, we examine how the choice of methods and data sources affect observed relationships between park accessibility and physical health, as measured through Body Mass Index (BMI). With a longitudinal study of the effects of neighborhoods on human development and cognitive aging as our …
Urban Income Mobility Patterns in the United States: 1980-2010
Wei Kang, Sergio Rey, Elijah Knaap
2020
'Spatial income inequality between neighborhoods within and across cities has been attractingsubstantive attention. As a static view cannot provide a complete picture for understanding thedriving processes of urbanization and spatial polarization, this paper turns its lens to spatial incomemobility, …
The Dynamics of Urban Neighborhoods: A Survey of Approaches for Modeling Socio-Spatial Structure
Elijah Knaap, Levi Wolf, Sergio Rey, Wei Kang, Su Han
2020
For close to a century, researchers from across the disciplines of Urban Studies have developed empirical models for understanding the spatial extent and social composition of urban neighborhoods–and how these dimensions change over time. Unfortunately, however, these techniques have often been …
Neighborhood change in the United States - a comparison of sequence analysis methods
Wei Kang, Sergio Rey, Levi Wolf, Elijah Knaap, Su Han
2020
There is a recent surge in research focused on urban trans- formations in the United States via empirical analysis of neighborhood sequences. The alignment-based sequence analysis methods have become the dominant techniques for the neighborhood sequence analysis. However, it is un- clear to what …
Machines Learn The Chicago School: Modeling Multidimensional Neighborhood Change as a Spatial Markov Process
Elijah Knaap, Sergio Rey, Levi Wolf, Nicholas Finio
2020
Despite lively interest and much active research, there remains little consensus on the appropriate ways to measure gentrification and neighborhood change, and even less on the best ways to model the phenomenon. In this paper, we enter the debate on gentrification by considering a novel model of …
Learning Geographical Manifolds: A Kernel Trick for Geographical Machine Learning
Levi John Wolf, Elijah Knaap
2020
Dimension reduction is one of the oldest concerns in geographical analysis. Despite significant, longstanding attention in geographical problems, recent advances in non-linear techniques for dimension reduction, called manifold learning, have not been adopted in classic data-intensive geographical …
Geosilhouettes: geographical measures of cluster fit
Levi Wolf, Elijah Knaap, Sergio Rey
2020
Regionalization, under various guises and descriptions, is a longstanding and pervasive interest of urban studies. With an increasingly large number of studies on urban place detection in language, behavior, pricing, and demography, recent critiques of longstanding regional science perspectives on …
Efficient Regionalization for Spatially-Explicit Neighborhood Delineation
Ran Wei, Sergio Rey, Elijah Knaap
2020
"Neighborhood delineation is increasingly relied upon in urban social science research to identify the most appropriate spatial unit. However, existing approaches for neighborhood delineation are either nonspatial or lead to noncontiguous or overlapping regions. In this paper, we propose the use of …
Comparative Segregation Analytics
Sergio Rey, Renan X. Cortes, Elijah Knaap
2020
Comparative segregation analysis holds the potential to provide rich in- sights into urban socio-spatial dynamics. However, comparisons of the lev- els of segregation between two, or more, cities at the same point in time complicated by different spatial contexts. The extent to which differences in …
An open-source framework for non-Spatial and Spatial segregation measures: the PySAL segregation module
Renan X. Cortes, Sergio Rey, Elijah Knaap, Levi John Wolf
2020
In urban geography and social sciences, segregation, usually consider five dimensions ina given society such as evenness, isolation, clustering, concentration and centralization. Allof these measure can either ignore spatial context or take it into consideration. Currently,several segregation …
A Visual Analytics System for Space-Time Dynamics of Regional Income Distributions Utilizing Animated Flow Maps and Rank-based Markov Chains
Sergio Rey, Su Han, Wei Kang, Elijah Knaap, Renan Cortes
2020
Regional income convergence and divergence has been an active field of research for more than twenty years, and research papers in this field are still being produced at a prodigious rate. Despite their importance for the study of dynamics of income distribution, interactive visualization tools …
Metropolitan planning in a vacuum: Lessons on regional equity planning from Baltimore’s Sustainable Communities Initiative
Nicholas Finio, Willow Lung-Amam, Gerrit-Jan Knaap, Casey Dawkins, Elijah Knaap
2019
The main policy initiative of the Obama administration’s first-term urban policy agenda was the Partnership for Sustainable Communities, which issued Sustainable Communities Regional Planning Grants (SCRPGs) to regions across the country. As participant activist scholars in the SCRPG planning …
How Do Cities Flow in an Emergency? Tracing Human Mobility Patterns during a Natural Disaster with Big Data and Geospatial Data Science
Su Yeon Han, Ming-Hsiang Tsou, Elijah Knaap, Sergio Rey, Guofeng Cao
2019
Understanding human movements in the face of natural disasters is critical for disaster evacuation planning, management, and relief. Despite the clear need for such work, these studies are rare in the literature due to the lack of available data measuring spatiotemporal mobility patterns during …
CATSLife: A Study of Lifespan Behavioral Development and Cognitive Functioning
Sally J. Wadsworth, Robin P. Corley, Elizabeth Munoz, B. Paige Trubenstein, Elijah Knaap, John C. DeFries, Robert Plomin, Chandra A. Reynolds, The CATSLife Team
2019
The purpose of this update is to provide the most current information about both the Colorado Adoption Project (CAP) and the Longitudinal Twin Study (LTS) and to introduce the Colorado Adoption/Twin Study of Lifespan behavioral development and cognitive aging (CATSLife), a product of their merger …
Adaptive Choropleth Mapper: An Open-Source Web-Based Tool for Synchronous Exploration of Multiple Variables at Multiple Spatial Extents
Su Yeon Han, Sergio Rey, Elijah Knaap, Wei Kang', Levi Wolf
2019
Choropleth mapping is an essential visualization technique for exploratory spatial data analysis. Visualizing multiple choropleth maps is a technique that spatial analysts use to reveal spatiotemporal patterns of one variable or to compare the geographical distributions of multiple variables. …
Spatio-temporal analysis of socioeconomic neighborhoods: The Open Source Longitudinal Neighborhood Analysis Package (OSLNAP)
Sergio Rey, Elijah Knaap, Su Han, Levi Wolf, Wei Kang
2018
The neighborhood effects literature represents a wide span of the social sciences broadly concerned with the influence of spatial context on social processes. From the study of segregation dynamics, the relationships between the built environment and health outcomes, to the impact of concentrated …
Opportunity for Whom? The Diverse Definitions of Neighborhood Opportunity in Baltimore
Willow S. Lung‐Amam, Elijah Knaap, Casey Dawkins, Gerrit‐Jan Knaap
2018
Across the United States, communities are increasingly interested in the spatial structure of opportunity. Recently, several federal programs have promulgated opportunity mapping as a tool to help increase disadvantaged communities' access to neighborhood opportunity. The increasing …
The Cartography of Opportunity: Spatial Data Science for Equitable Urban Policy
Elijah Knaap
2017
As evidence on the contextual effects of place upon individual outcomes has become increasingly solid over time, so too have urban policies and programs designed to connect underserved people with access to spatial opportunity. To this end, many attempts have been made to quantify the geography of …
Who Moves to Opportunity? Spatial Returns to Housing Assistance and the Effect of Specialized Mobility Programs
Elijah Knaap
2016
In the following paper, I examine the residential trajectories of housing choice voucher holders in the Baltimore metropolitan region. For decades, the Baltimore region has been a laboratory for housing mobility policies, having participated in the Moving to Opportunity experiment during the 1990s …
Housing Assistance in Black and White: A Discrete Choice Model of Residential Sorting in Housing Voucher Programs
Elijah Knaap
2016
This study uses a series of discrete choice models to study residential sorting patterns of housing choice voucher (HCV) holders in the Baltimore Metropolitan Region. Using data from 50,000 voucher holders and 800,000 residential parcels, I examine which spatial characteristics influence the …
Polycentrism as a Sustainable Development Strategy: An Empirical Analysis from the State of Maryland
Elijah Knaap, Chengri Ding, Yi Niu, Sabyasachee Mishra
2015
We present in this paper an analysis of economic centers and their role in shaping employment development patterns and travel behavior in the state of Maryland. We begin by identifying 23 economic centers in the Baltimore-Washington region. We then examine these centers first in their role as …
Driving to Opportunity: Understanding the Links among Transportation Access, Residential Outcomes, and Economic Opportunity for Housing Voucher Recipients
Rolf Pendall, Christopher R. Hayes, Taz George, Zachary J. McDade, Casey Dawkins, Jae Sik Jeon, Elijah Knaap, Evelyn Blumenberg, Gregory Pierce, Michael Smart
2014
In the 1990s and early 2000s, the Department of Housing and Urban Development sponsored two major experiments to test whether housing choice vouchers propelled low-income households into greater economic security, the Moving to Opportunity for Fair Housing program (MTO) and the Welfare to Work …
A tool for measuring and visualizing connectivity of transit stop, route and transfer center in a multimodal transportation network
Sabyasachee Mishra, Timothy F. Welch, Paul M. Torrens, Cheng Fu, Haojie Zhu, Elijah Knaap
2014
Agencies at the federal, state and local level are aiming to enhance the public transportation system (PTS) as one alternative to alleviate congestion and to cater to the needs of captive riders. To effectively act as a viable alternative transportation mode, the system must be highly efficient. One …