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Raised in Paris, Vincent Rollet encountered the world outside France early in his life. His father, an engineer, traveled globally to establish electrical infrastructure, relocating the family to the United States for two years when Rollet was a young child. His father’s profession ignited Rollet’s passion for international development and progress. “It made me eager to explore and understand how things function in various places across the globe,” he states.
Currently, Rollet is a fifth-year PhD candidate in MIT’s Department of Economics, investigating how cities transform — and how their historical foundations can constrain them. “Cities constantly need to evolve with economic shifts,” he elaborates. “For instance, as populations expand, there may be a need for increased housing, or the desire to convert manufacturing areas into contemporary lab spaces. With remote work becoming more common, numerous cities now have surplus office areas that could potentially be turned into residential units.” Ultimately, Rollet aspires for his research to impact urban policymakers, allowing them to better cater to city inhabitants.
A fortunate coincidence
Rollet’s initial encounter with economics was nearly by chance. As a teenager, he stumbled upon lecture videos from a game theory course at Yale University. “I randomly clicked on the available courses,” he recalled, “and I watched the lectures and found them intriguing.”
During high school and college, he concentrated on mathematics and physics. “That’s the form of training typically encouraged in France,” he mentions. However, at the conclusion of his first year at École Polytechnique — where military training is mandatory for all students — he recollected the Yale course he watched during high school. That year, he had been involved in a military service program for underprivileged youth. “I was seeking an enjoyable way to resume my studies,” he shares. “So I returned to game theory.”
Rollet opted to enroll in a game theory class taught by economics professor Pierre Boyer, who would significantly influence his academic journey. Through discussions with Boyer, Rollet discovered that economics could offer a rigorous, mathematical methodology to comprehend the subjects surrounding international development and global politics that had long captivated him. Boyer introduced Rollet to two economists educated at MIT, professors Vincent Pons and Benjamin Marx, with whom he continues to collaborate. A research visit to the U.S. in 2019 to work with them cemented his enthusiasm for pursuing graduate studies. Shortly afterward, he commenced his PhD at MIT.
Why cities become “stagnant”
Rollet’s research investigates the reasons cities find it challenging to adapt their built environments amid shifting economic conditions, and why specific urban areas become “stagnant” in outdated patterns of growth. He is attracted to cities as they represent a microcosm of various interacting economic systems. “To comprehend cities, you must understand how labor markets operate, how the housing market functions, and how transportation systems work,” he emphasizes.
Rollet has devoted the majority of his PhD studies to New York City. By analyzing comprehensive data on building permits, real estate transactions, rental prices, and zoning modifications, he has tracked the development of every building in the city over nearly two decades, investigating when and why developers opt to demolish structures and construct new ones, and how these choices are shaped by economic, regulatory, and technological limitations. By merging computational theories and data — which often incorporates insights into natural experiments (i.e., What occurs when a city alters a regulation?) — Rollet aims to uncover universal principles underlying urban growth and evolution.
Originally designed as a manufacturing center with dense commercial hubs and sprawling residential peripheries, New York’s physical configuration has remained largely unchanged since zoning regulations were enacted in the 1960s. Despite significant changes in population and economic activity, the city’s regulations have scarcely shifted, causing considerable mismatches: skyrocketing housing prices, overcrowded residential sectors, and underused commercial spaces. The buildings are costly to replace, and regulations are notoriously difficult to amend once established.
Rollet’s research uncovers significant inefficiencies. In cities like New York or Boston, housing frequently sells for hundreds of thousands of dollars above the actual construction cost. This substantial disparity indicates that demand vastly exceeds supply: there simply aren’t enough homes being produced. “When the housing supply is overly restricted, we are essentially squandering resources, making housing unnecessarily costly,” he elucidates.
However, implementing any sort of action or policy to mitigate these inefficiencies has repercussions. For instance, it can produce varied impacts on different demographics. “There will be beneficiaries and those who lose out,” Rollet clarifies. “One reason is that you may directly care about the welfare of a particular demographic, such as providing housing for lower-income households. Another reason is that if there are a significant number of individuals negatively affected by a certain policy, or if they hold enough power, they could potentially obstruct the policy change, presenting a political obstacle.”
So what causes a city to become “stagnant”? “Much of the time,” Rollet reflects, “it’s policy.” Yet, the consequences of policy changes require time to materialize and may be difficult for individuals to perceive. Rollet references Cambridge’s recent zoning reform that permits the construction of six-story buildings as an illustrative example. “These policy modifications can benefit a multitude by slightly decreasing housing prices for everyone,” he notes, “but individuals may not be aware of this. This renders collective action challenging.”
Economics, nonetheless, offers a toolkit to define and quantify these effects. “What economists can contribute is providing policymakers with more information regarding the probable repercussions of their policy actions,” Rollet explains.
Aiming to “enhance circumstances”
As Rollet approaches the final stages of his PhD, he feels thankful to his mentors in the economics department for aiding him in establishing a foundation for the various tools essential for his work. From professors Dave Donaldson and David Atkin, he learned how to modify methods typically applied in international trade analysis to assess the movement of people across neighborhoods and cities. From Professor Tobias Salz, he acquired insights into modeling firm behavior over time, which he currently applies to understand the actions of real estate developers. “The training here pushes you to produce research that truly distinguishes itself,” he remarks. “The courses guided me in discovering new areas and methods.”
In addition to research, Rollet actively engages in his department, including serving as the co-president of the Graduate Economics Association. “MIT truly represents the pinnacle of economics, not just due to their curriculum but because it’s a genuinely collaborative department where individuals support one another,” he notes. “The Graduate Economics Association fosters that community spirit, and I wanted to participate in that.” Additionally, he is a member of a mental wellness and peer support group within the department.
Rollet also finds joy in teaching. He has served as a teaching assistant for microeconomics and international trade courses and has amassed an impressive writing portfolio that clarifies complex ideas across various fields. In high school, one of Rollet’s pastimes was crafting quantum theory explainers online for general audiences. Several publishers discovered his writing and reached out about turning it into a book. The book was published and has sold over 14,000 copies. While in college, Rollet collaborated on two books: one focusing on game theory for general audiences and an introductory economics textbook that two professors recruited him to co-author. It remains the standard textbook at École Polytechnique today. “It was my Covid project,” Rollet laughs.
Looking ahead, Rollet aspires to pursue a career in research and education. His immediate objective remains clear: to generate research that meaningfully impacts policy by illuminating how cities can transcend constraints and evolve in ways that better benefit their populations. He is enthusiastic about how, in the future, more granular and detailed data sources could reveal how micro-level behaviors can lead to macro outcomes.
“Housing and urban spaces — these markets are failing significantly in numerous regions worldwide. There’s genuine potential for policy to enhance circumstances.”
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