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Northwestern University

Transportation Policy

Systematic Approach to Evaluate the State of Illinois’ Preparedness for Smart Mobility

Researcher(s): Angeli Jayme (UIUC), Berkan Usta (UIUC), Divyakant Tahlyan, Breton Johnson, Hani Mahmassani, Imad L. Al-Qadi, and Jerry Quandt
Year: 2024

Connected, automated, shared, and electric (CASE) technologies are shaping Mobility 4.0—a connected, digitized, multimodal, and autonomous system of systems that is challenging past and existing strategic transportation planning practices at state and local levels. A systematic approach is presented to aid transportation agencies in their planning needs to evaluate preparedness for smart mobility. Guided by a set of online surveys, interviews, and workshops conducted among different stakeholders, this paper identifies strengths and opportunities to leverage the state’s public, private, and academic sector resources to prepare agencies in realizing the potential opportunities of Mobility 4.0 technologies, while avoiding possible pitfalls in the process. Seven smart mobility pillars were identified and ranked through a balanced scorecard analysis in this study for Illinois—namely (in decreasing order of importance), alternative fuels, scaling intelligent transportation systems, connected and automated (CA) freight, farm automation, CA logistics, insurance, and urban mobility. Tactical focus areas were also identified for each pillar and prioritized with suggested leads and stakeholders to champion the CASE directives and opportunities. Near-term actions were also suggested that included establishing a central structure for Illinois’ CASE program, enriching the knowledge base and experience, preparing the transportation infrastructure, partnerships with external stakeholders, and expansion of laws, regulations, and policies that will help administer and grow CASE technology deployment and integration.

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Mitigating traffic congestion induced by transportation network companies: A policy analysis

Researcher(s): Kenan Zhang, Yu (Marco) Nie 
Year: 2022

This paper analyzes and evaluates several policies aiming to mitigate the congestion effect a Transportation Network Company (TNC) brings to bear on an idealized city that contains a dense central core surrounded by a larger periphery. The TNC offers both solo and pooling e-hail services to the users of public transport. We develop a spatial market equilibrium model over two building blocks: an aggregate congestion model that describes the traffic impact of TNC operations on all travelers in the city, including private motorists, and a matching model that estimates the TNC's level of service based on the interactions between riders and TNC drivers. Based on the equilibrium model, we formulate and solve the optimal pricing problem, in which the TNC seeks to optimize its profit or social welfare subject to regulatory costs and/or constraints. Three congestion mitigation policies are implemented in this study: (i) a trip-based policy that charges a congestion fee on each solo trip starting or ending in the city center; (ii) a cordon-based policy that charges TNC vehicles entering the city center with zero or one passenger; and (iii) a cruising cap policy that requires the TNC to maintain the fleet utilization ratio in the city center above a threshold. Based on a case study of Chicago, we find TNC operations may have a significant congestion effect. Failing to anticipate this effect in the pricing problem leads to sub-optimal decisions that worsen traffic congestion and hurt the TNC's profitability. Of the three policies, the trip-based policy delivers the best performance. It reduces traffic congestion modestly, keeps the TNC's level of service almost intact, and improves overall social welfare substantially. The cruising cap policy benefits private motorists, thanks to the extra congestion relief it brings about. However, because other stakeholders together suffer a much greater loss, its net impact on social welfare is negative. Paradoxically, the policy could worsen the very traffic conditions in the city center that it is designed to improve.

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Pareto Efficiency Analysis of Private Toll Road Networks

Researcher(s): Hang Shu. Pablo L. Durango-Cohen
Year: 2022

We consider the problem of setting tolls and capacities in transportation networks serving single origin-destination markets. The motivation is to understand the effects of network structure and of decentralized decision-making on the performance of such systems, as well as to identify opportunities for government intervention. Performance, in this case, refers to social welfare and profits, with the latter determining private firms' incentives to participate in road operation. We first extend the Pareto efficiency analysis appearing in the literature for the single road case. Specifically, we consider a network operated by a single firm and show that aggregate Pareto-efficient capacity levels provide the same service quality as in the single road case and that any convex combination of social welfare-maximizing and profit-maximizing route tolls can be Pareto efficient, suggesting that such outcomes can arise naturally from negotiations between a government and a private operator. In the second part of the paper, we consider a market where, following bilateral negotiations with a government, self-interested, private operators set tolls and capacities independently. Again, we show that the optimal capacity for each link is set to achieve the same service level as that in the single road case. Further, we adapt the concept and show that decentralized Pareto-efficient tolling strategies are bounded. Characterization of Pareto-efficient tolling and capacity strategies for the two benchmark cases reveals when (government) interventions can lead to increased social welfare, operator profit, or both. As an example, we analyze simple stage networks and, among other results, show that, even under bilateral negotiations and decentralized decision-making, sufficient competition can lead to aggregate Pareto efficiency.

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For whom did telework not work during the Pandemic? understanding the factors impacting telework satisfaction in the US using a multiple indicator multiple cause (MIMIC) model

Researcher(s): Divyakant Tahlyan, Maher Said, Hani Mahmassani, Amanda Stathopoulos, Joan Walker, Susan Shaheen
Year: 2022

The COVID-19 pandemic required employees and businesses across the world to rapidly transition to work from home over extended periods, reaching what is likely the upper bound of telework in many sectors. Past studies have identified both advantages and disadvantages of teleworking. The pandemic experience offers a unique opportunity to examine employees’ experiences and perceptions of telework given the broad participation duration and extent. While employer strategies will play a major role in defining the future forms and adoption of telework, employee preferences and constraints, such as access to appropriate technology to work from home or the home environment, are also going to be important factors. Using data from a U.S. representative sample of 318 working adults, this study uses a Multiple Indicator Multiple Cause Model (MIMIC) to understand employee satisfaction with telework. The presented model links telework satisfaction with experienced and perceived benefits and barriers related to telework, and hence provide a causal structure to our understanding of telework satisfaction. We also present an ordered probit model without latent variables that help us understand the systematic heterogeneity in telework satisfaction across various socio-demographic groups. The results suggest younger and older aged individuals experienced/perceived lower benefits and higher barriers to teleworking compared to middle aged individuals. The results also suggest a disproportionate impact on Hispanic or Latino and Black respondents as well as on those with children attending online school from home. Accordingly, this study highlights important factors impacting telework adoption that employers and policy makers should consider in planning future work arrangements and policies in a post-pandemic world.

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To pool or not to pool: Equilibrium, pricing and regulation

Researcher(s): Kenan Zhang, Yu (Marco) Nie
Year: 2021

We study a transportation network company (TNC) that offers on-demand solo and pooling e-hail services in an aggregate mobility service market, while competing with transit for passengers. The market equilibrium is established based on a spatial driver–passenger matching model that determines the passenger wait time for both solo and pooling rides. We prove, under mild conditions, this system always has an equilibrium solution. Built on the market equilibrium, three variants of pricing problems are analyzed and compared, namely, (i) profit maximization, (ii) profit maximization subject to regulatory constraints, and (iii) social welfare maximization subject to a revenue-neutral constraint. A comprehensive case study is constructed using TNC data collected in the city of Chicago. We found pooling is desirable when demand is high but supply is scarce. However, its benefit diminishes quickly as the average en-route detour time (i.e., the difference between the average duration of solo and pooling trips) increases. Without regulations, a mixed strategy—providing both solo and pooling rides—not only achieves the highest profit and trip production in most scenarios, but also gains higher social welfare. The minimum wage policy can improve social welfare in the short term. However, in the long run, the TNC could react by limiting the size of the driver pool, and consequently, render the policy counterproductive, even pushing social welfare below the unregulated level. Moreover, by maintaining the supply and demand of ride-hail at an artificially high level, the minimum wage policy tends to exacerbate traffic congestion by depressing the use of collective modes (transit and pooling). A congestion tax policy that penalizes solo rides promotes pooling, but may harm social welfare. However, it promises to increase both social welfare and pooling ratio when jointly implemented with the minimum wage policy.

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Investigating the interconnectedness of active transportation and public transit usage as a primer for Mobility-as-a-Service adoption and deployment

Researcher(s): Alec Biehl, Amanda Stathopoulos
Year: 2020

Background: With the advent of Mobility-as-a-Service packages to reduce car usage and (by extension) greenhouse gas emissions, it is crucial that researchers and practitioners consider mutual determinants and outcomes that link the adoption of multiple alternative modes. This study therefore investigates the joint usage of active travel (walking, cycling, bike-sharing) and public transit (bus, rail) modes with respect to personal and situational contexts. Methods: Online survey data (n = 826) were collected across six Midwestern U.S. states using Amazon MTurk. Respondents indicated their average weekly usage of eight travel modes across three trip purposes so that multimodality could be assessed. Several psychological constructs were extracted via (a) the stages of change framework, used to indicate willingness to adopt new behavior, and (b) confirmatory factor analysis conducted on Likert scales rooted in theories of community, identity, norms, personality, and well-being. A multiple-indicators multiple-causes structural equation model is then employed to investigate the process of adopting a modality style that incorporates active and transit modes. Results: The model confirms that compatible physical and social contexts, as well as navigational skills and openness to learning, are key primers of multimodalism. However, a path juncture stemming from neighborhood support for mobility innovation illustrates a potential polarity in outcomes between individuals and communities. In addition, the stage of active mobility adoption is linked to identity and norm activation, offering further guidance on what influences readiness for change. Conclusions: The seamless integration of mobility services is critical to matching the convenience and comfort of the private vehicle; understanding potential pathways to sustainable mobility, though, requires analyses and interventions that are driven by well-being outcomes and grounded in rigorous psychological frameworks. The research findings offer practical guidance for identifying intervention opportunities to be linked with MaaS enrollment while demonstrating the need to illuminate how mobility might relate to social cohesion, identity expression, and various sources of satisfaction.

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Operational benefits and challenges of shared-ride automated mobility-on-demand services

Researcher(s): Michael Hyland, Hani S. Mahmassani
Year: 2020

This paper presents a quantitative analysis of the operations of shared-ride automated mobility-on-demand services (SRAMODS). The study identifies (i) operational benefits of SRAMODS including improved service quality and/or lower operational costs relative to automated mobility-on-demand services (AMODS) without shared rides; and (ii) challenges associated with operating SRAMODS. The study employs an agent-based stochastic dynamic simulation framework to model the operational problems of AMODS. The agents include automated vehicles (AVs), on-demand user requests, and a central AV fleet controller that can dynamically change the plans (i.e. routes and AV-user assignments) of AVs in real-time using optimization-based control policies. The agent-based simulation tool and AV fleet control policies are used to test the operational performance of AMODS under a variety of scenarios. The first set of scenarios vary user demand and a parameter constraining the maximum user detour distance. Results indicate that even with a small maximum user detour distance parameter value, allowing shared rides significantly improves the operational efficiency of the AV fleet, where the efficiency gains stem from economies of demand density and network effects. The second set of scenarios vary the mean and coefficient of variation of the curbside pickup time parameter; i.e. how long an AV must wait curbside at a user's pickup location before the user gets inside the AV. Results indicate that increases in mean curbside pickup time significantly degrade operational performance in terms of user in-vehicle travel time and user wait time. The study quantifies the total system (user plus fleet controller) cost as a function of mean curbside pickup time. Finally, the paper provides an extensive discussion of the implications of the quantitative analysis for public-sector transportation planners and policy-makers as well as for mobility service providers.

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Trading off costs, environmental impact, and levels of service in the optimal design of transit bus fleets

Researcher(s): Pablo L. Durango-Cohen, Elaine C. McKenzie
Year: 2018

The development of a systematic framework to support the design of transit bus fleets is justified by the significant and long-lasting implications associated with decisions to purchase transit vehicles, as well as by developments in fuel propulsion and battery technologies over the last 2 decades that have increased the options available to transit operators, and, in turn, the complexity of assessing the corresponding tradeoffs. The need to evaluate these tradeoffs is, in part, driven by the emergence of environmental impact mitigation, i.e., emissions reductions, as a critical concern of transit operators and governments around the world. To address these concerns, we present an optimization model to support the design of transit bus fleets while accounting for costs, level-of-service requirements, and environmental impact. Methodologically, the work bridges applications of Economic Input-Output analysis to conduct environmental lifecycle assessment, with seminal work in production economics. We apply the framework to support design of bus fleets consisting of 4 bus types differing in their fuel-propulsion technology: ultra-low sulfur diesel, hybrid diesel-electric, compressed natural gas, and hydrogen fuel-cell. The 4 bus types were assessed in the National Renewable Energy Laboratory transit bus evaluation and demonstration studies conducted over the period 2003–2009. The nominal problem herein is to minimize acquisition, operation and disposal costs. Constraints in the model are used to impose a minimum frequency of service, i.e., headway, and to ensure that route capacity satisfies passenger demand. Environmental impact is considered along the following dimensions: energy consumption, and emissions of greenhouse gasses, particulate matter, and nitrous oxides. Results show that fleet heterogeneity increases in scenarios where demand fluctuates, i.e., peak vs. off-peak. Perhaps even more interesting, we show how the dual/shadow prices provide a (monetary) measure of the tradeoffs among level of service and environmental impact, and discuss how they can be used to obtain robust fleet configurations.

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Information System for Infrastructure Deployment in Support of Future Vehicles

Researcher(s): Diego Klabjan
Year: 2010

Mass production electric vehicles (EVs) will be coming on the market en masse during the next few years. Their adoption will depend on the availability of charging stations. A few cities have started deploying such stations and many are in the planning stage. The decision makers, being city governments, utilities, or private entities such as mall and fast-food restaurant operators, are in need of information systems that will assist them in deploying such an infrastructure, including (1) EV demand consideration, (2) the actual location of stations, (3) the implied service time on car owners, and (4) power grid implications. All of these aspects should be addressed through analytical methodologies, such as discrete choice modeling to capture the demand, optimization for actual location recommendations, and comprehensive simulations to estimate the overall impact on the system. While some of these questions have already been addressed at the macro level, thorough research is required to conduct assessments at the micro level, which is required to actually build the infrastructure.

The developed decision support system and service will be subscription based with a broad market spreading from city governments and municipalities (installing charging stations in public parking spaces, curbside charging), utilities, and private entities (retailers, mall operators, fast-food and restaurant chains, garage owners, etc.). While the actual savings of using analytics for deployment vs. more judgmental approaches are hard to estimate, the proposed system will drastically reduce labor needs, and it will open the door to easily conduct what-if analyses.

The initial phase of the project will be focused on developing such a system for the EVs, however the underlying concepts and methodologies are also applicable to deploying the infrastructure of other possible alternative fuel vehicles (compressed natural gas (CNG), hydrogen, biofuel stations).

A Comment on "Subsidization of Urban Public Transport and the Mohring Effect"

Researcher(s): Ian Savage
Year: 2010

Van Reeven (2008) argues that the Mohring effect is not relevant to the determination of transit subsidies because a profit-maximizing monopolist would supply frequencies that are the same as, or greater than, those that are socially optimal. We find that his results depend on the reduction or elimination of the effect of fares on demand, causing optimal prices to be indeterminate within broad ranges. Consequently, his model is an unsatisfactory tool for discussing subsidies in general, and the optimal combination of fare and frequency in particular.

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A Structural Model of Safety and Safety Regulation in the Truckload Trucking Industry

Researcher(s): Ian Savage
Year: n/a

This research models the effects of various public policies to improve safety within a structural model of the trucking industry.  The structural model describes how trucking firms choose their level of safety by balancing the cost of preventing crashes against the financial consequences of a crash.  This choice occurs within an interregional trade model that sets the market prices and quantities for the commodities that are transported between geographically dispersed markets.  After specifying the first-best, full-information equilibrium, the research models the effects of two common market failures. The first is the myopic underestimation of crash costs by some trucking firms.  The second is a more general problem that some of the external costs of truck crashes (such as congestion at the crash site) cannot be legally recovered from trucking firms.  The research then investigates the choice of policies to protect other road users, and those who live along the highway, from these market failures.  The effects of the imposition of a minimum safety standard are compared with the consequences of either levying post-crash fines, or the charging of an ex-ante tax on the trucking industry.  The different policies are ranked on the basis of both their economic desirability, and the likelihood that they will be selected by voters in a political economy.

Communication Matters: Communicating the Value of Transportation Research

Researcher(s): Johanna P. Zmud, Julie L. Paasche, Mia Zmud, Timothy J. Lomax, Joseph L. Schofer, Judy A. Meyer
Year: 2009

This comprehensive document provides transportation researchers, planners, managers, and others with professional advice on how to design, plan and execute effecting communication campaigns that convey the value of research projects or programs. It covers the elements of good communication practices, the communication process, evaluation and feedback, and targeting specific audiences. This is a practical document, offering quick tips, detailed how-to descriptions, and useful resources and templates. The guidebook is organized into the following four chapters and two appendices: (1) Signs of Good Communication Practices; (2) The Communication Process; (3) Planning and Evaluating Your Research Communication; (4) Putting It All Together: Communicating to Specific Audiences; (Appendix 1) Transportation Case Studies; and (Appendix 2) Non-Transportation Best Practices.

Summary: Extensive research and examination of best practices in communication, within and outside of the transportation community, informed NCHRP Report 610, Communicating the Value of Transportation Research – Guidebook. The research assembled practical tips, a model process, case studies, and examples of good communication methods that all transportation researchers can use. The guide is organized into four chapters and two appendixes to explain the process:

Chapter 1: Signed of Good Communication Practices presents seven indicators drawn of best practices inside and outside of the transportation community.

Chapter 2: The Communication Process explores the key steps for planning, talking about, writing, and creating the context, strategy, and content, and choosing the appropriate channels – media and contacts – and style.

Chapter 3: Planning and Evaluating Your Research Communication presents ways to understand how target audiences will hear the message.

Chapter 4: Putting It All Together: Communicating to Specific Audiences provides examples of how to communicate with audiences that matter: research peers, transportation policy and program officials, legislative leaders and staff, the news media, and the public.

Appendix 1: Transportation Case Studies illustrates good communication practices through experiences from seven transportation research projects.

Appendix 2: Nontransportation Best Practices summarizes the approaches of four organizations that have excelled in communicating the value of research.

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Information Assets to Support Transportation Decision Making: Report of a Peer Exchange of State Transportation Organizations

Researcher(s): Joseph L. Schofer
Year: 2007

This circular summarizes discussions at a peer exchange of state department of transportation officials and other professionals that focused on data and information uses, management strategies, needs, and gaps in their organizations. The peer exchange examined the role of data and information in transportation decision making; identified information resources, gaps, and opportunities; and explored data, access, and analysis improvements for information resource programs. In addition, participants discusses possible strategies that the transportation community might use to implement such improvements.

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Characterizing Neighborhood Pedestrian Environments with Secondary Data

Researcher(s): James R. Parks, Joseph L. Schofer
Year: 2006

Commonly used measures of the pedestrian environment rely on field data collection and subjective judgments. This study develops objective measures of the pedestrian environment that use secondary data or plans for proposed neighborhoods and still correlate well with accepted subjective measures. Data to estimate these measures, describing network design, sidewalk availability and building accessibility, were collected for a sample of neighborhoods in the Chicago area using both common secondary sources and subjective field surveys. Linear regression was used to estimate judgmental indices with the laboratory data as independent variables. The measures developed can be substituted for subjective field measures to reduce costs with minimal loss in accuracy and to characterize walkability of proposed neighborhood designs.

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The Colorado Revenue Limit: The Economic Effects of TABOR

Researcher(s): Therese J. McGuire, Kim S. Reuben
Year: 2006

In November 2005, Colorado residents voted to suspend for five years the state’s self-imposed revenue caps as outlined in the state’s Taxpayer Bill of Rights (TABOR). TABOR, which was passed as a constitutional amendment in 1992, limits the growth rate of revenue to population growth and inflation. The effects of TABOR on government spending and economic growth have been hotly debated in recent years. Proponents attribute much of Colorado’s economic prosperity in the period immediately following adoption of the law to the limit and its effect on government spending and taxes. Opponents of TABOR argue that TABOR-induced reductions in government spending have led to curtailed government services, including those that voters and businesses care more about.

To understand TABOR’s effect on Colorado’s economic health and growth, we compare Colorado with other states, controlling for prior history and economic and demographic characteristics in order to disentangle the effects of TABOR from other factors influencing Colorado’s economic performance.

We begin with a description of TABOR and Referendum C, the measure enacted in November 2005 that suspended TABOR for five years and modified some of TABOR’s requirements. We compare TABOR to tax and expenditure limits (TELs) in other states. TABOR is by many measures the most binding TEL in the country. We also describe how TABOR interacts with other Colorado budget rules. We then describe the mechanism by which TELs might strengthen local and regional economies, and review the extensive empirical literature on both the effect of TELs on taxes and spending and on the effect of taxes on business location and economic growth. The meat of our analysis compares the growth rate of personal income and employment in Colorado with the growth rates in other states in the periods before and after passage of TABOR. While we find some very limited evidence for short-term increases in growth, those were not sustained in the longer term. The lack of a sustained effect holds up after controlling for economic and demographic characteristics of the states. The results of those analyses show that there is little empirical support for the notion that TABOR had a positive effect on Colorado’s economy.

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Illinois's Individual Income Tax and General Sales Tax: Options for Reform

Researcher(s): Richard F. Dye, Therese J. McGuire
Year: 2005

Richard F. Dye, Lake Forest College, and Therese J. McGuire, Northwestern University, look at Illinois’s individual income and general sales taxes; they suggest changes such as including retirement income in the tax base and ending the exemption for food sales. Illinois should also tax services, the authors suggest.

Multicentered Chicago

Researcher(s): Henry C. Binford
Year: 2005

Chicagoans like to think of their home as “multiethnic,” or as “the city of neighborhoods.” Indeed, the celebration of neighborhood is one of the binding rituals of Chicago culture. The shelves of local bookstores are crammed with neighborhood guides of various sorts, and in the 1990s Mayor Richard M. Daley harnessed neighborhood consciousness to the marketing of tourism, officially defining certain well-known districts with banners, signs, and dramatic arches. When visitors come to the city one of the things they frequently ask to see is “Chicago's ethnic neighborhoods.” Yet every big city in America is a city of neighborhoods—forged by migration, work patterns, race, religion, and other factors in addition to ethnic culture. Boston, San Francisco, and many other cities have their own rich patterns of colorful locales. What, if anything, makes Chicago's multicentered settlement pattern distinctive? Answering that question requires setting aside notions of neighborhood geography and diversity that became widespread in the mid-twentieth century but have been challenged by recent scholarship. It requires looking beyond the notion of “neighborhood” itself, as that term has been commonly and vaguely used, and thinking about Chicago's many spatial subcommunities as changing manifestations of history and human initiative. It requires looking deeper into Chicago's past, recognizing how the city's growth fits into the long history of national urbanization, and defining certain features of Chicago's development that were unusual.

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Strategic Ideas for a Prosperous Africa

Researcher(s): Richard Joseph
Year: 2005

Numerous meeting were convened in many countries to discuss the issues being considered by the Council on Africa sponsored by the British Government. This essay is an expanded version of my responses to questions sent to invited participants in a meeting convened by the Council of Foreign Relations in New York. They are based on my research and published writings, and those of many colleagues, over the past three decades.

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Are Property Tax Limitations More Binding over Time?

Researcher(s): Richard F. Dye, Therese J. McGuire, Daniel P. McMillen
Year: 2005

In 1991, a property tax limitation measure was imposed in five Illinois counties. Die and McGuire (1997) studied its short-term impact. With the limit now in effect for over a decade and extended to many more counties, we assess its long-term impact. Because jurisdictions brought under the limitation since 1997 have done so after a county-option referendum, our estimation strategy treats the measure as endogenous. We find that the restraining effect of the limit on the growth of property taxes is stronger in the long run than the short run, and that the growth of school expenditures is slowed by the measure.

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