MIT System Dynamics Seminar | If Vensim is the Answer, What is the Question?
Please visit the MIT System Dynamics Seminars page for more information.
You are invited to attend the System Dynamics Seminar being held on Friday, October 20th from 12:30-2:00pm EST in the Jay W. Forrester conference room, E62-450, or via Zoom: https://mit.zoom.us/j/98105285349 (Password: SDFA23). Our guest speakers will be Tom Fiddaman (Ventana Systems) and Angie Moon (MIT Civil & Environmental Engineering) presenting If Vensim is the answer, what is the question? Reflecting on the future direction of the System Dynamics tool and user ecosystem (see abstract below, announcement attached). Lunch will be provided to those attending in person and a reminder email will be sent out closer to the date.
If you would also like to schedule a 30-minute 1:1 meeting with Tom before or after the seminar, please fill out the following Doodle poll by COB Tuesday, October 17th and I will confirm times and location with a calendar invite: https://doodle.com/meeting/participate/id/e09LyWya.
Abstract
Once upon a time, data was scarce, simulation was nearly unheard of, there were few ways to build and use quality dynamic models, and models rarely gave direct input to decisions. This made it easy for tool builders and tool users to coevolve within their own disciplinary stovepipes. The scale of our problems, and hopefully our opportunities, means that isolation is no longer viable. System Dynamics modelers can increasingly benefit from new tools in data science, AI and machine learning, and many fields could benefit from SD knowledge guiding better dynamics, realistic behavior, and useful interaction with decision makers.
Our future could be bright, with AI assistants freeing modelers from boring tasks, raising the productivity of thinking about systems, and making model results accessible to users. Or, it could be dark, with “ChatMDL” rapidly generating the simulation equivalent of 3-legged chicken images, models with superficial validity but more propaganda value than predictive accuracy, faster than we can debunk them.
In this seminar, I’d like to explore the state of the System Dynamics tool portfolio and the requirements of modelers and model consumers. In passing, I will mention the near-term roadmap for Vensim, as well as the broader ecosystem of SD tools many of us use. But the real goal is to discuss the long-term vision for System Dynamics. How do we realize a future in which:
- it’s easy to make every model a Bayesian blend of structure and parameter priors from subject matter expertise and data likelihoods?
- aggregation is not a dark art, but automated in a flexible and principled way?
- every model run is a synthetic data experiment supporting decision making under uncertainty?
- support for exploration of the state space yields as much understanding as we get from analytical methods on simple models?
- we have the computing power to support these innovations, and
- we can explain what we’re doing to influence people to solve our biggest problems.
MIT System Dynamics Seminar | Institutional Ensembles and Cultural Institutional Capacity
Please visit the MIT System Dynamics Seminars page for more information.
You are invited to attend the System Dynamics Seminar being held on Friday, October 13th from 1:00-2:30pm EST (please note the time change) in the Jay W. Forrester conference room, E62-450, or via Zoom: https://mit.zoom.us/j/98105285349 (Password: SDFA23). Our guest speaker will be Scott E. Page (University of Michigan) presenting Institutional Ensembles and Cultural Institutional Capacity (see abstract and brief bio below, announcement and paper attached). Lunch will be provided to those attending in person and a reminder email will be sent out closer to the date.
If you would also like to schedule a 30-minute 1:1 meeting with him before or after the seminar, please fill out the following Doodle poll by COB Friday, October 6th and I will confirm times and location with a calendar invite: https://doodle.com/meeting/participate/id/dPYN5qAe. Please notify me if you need to meet over Zoom instead.
Abstract
We construct a series of models within a systems framework to analyze the interdependence between a society’s composition of institutions and its cultural-institutional capacity: the knowledge, behaviors, beliefs, norms, and networks that enables institutions to operate. In our models, a society selects a mixture of institutions of various types to allocate resources and take actions. These include markets, hierarchies, democracies, community-based institutions, or even algorithms. These institutional choices contribute to the production of cultural-institutional capacity, and, conversely, cultural-institutional capacity influences how well each institutional type performs. Cultural-institutional capacity building can be self-reinforcing. Markets can produce greater capacity for markets. It can also be generic and improve all institutional types. Neither of these forms of capacity building necessarily produces efficient ensembles of institutions. Paradoxically, systems with both forms can result in the collapse of an institutional type that builds generic capacity.
About the Presenter
Scott E. Page is the John Seely Brown Distinguished University Professor of Complexity, Social Science, and Management at the University of Michigan, and the Williamson family Professor of Business Administration, professor of management and organizations, Stephen M. Ross School of Business; professor of political science, professor of complex systems, and professor of economics, LSA. In 2011, he was elected to the American Academy of Arts and Sciences. Read more here.
MIT System Dynamics Seminar | A Replication Study of Operations Management Experiments in Management Science
Please visit the MIT System Dynamics Seminars page for more information.
You are invited to attend the System Dynamics Seminar being held on Friday, October 6th from 12:30-2:00pm EST in the Jay W. Forrester conference room, E62-450, or via Zoom: https://mit.zoom.us/j/98105285349 (Password: SDFA23). Our guest speaker will be Jordan Tong (Wisconsin School of Business) presenting A Replication Study of Operations Management Experiments in Management Science (see abstract and brief bio below, announcement and paper attached). Lunch will be provided to those attending in person and a reminder email will be sent out closer to the date.
If you would also like to schedule a 30-minute 1:1 meeting with him before or after the seminar, please fill out the following Doodle poll by COB Friday, September 29th and I will confirm times and location with a calendar invite: https://doodle.com/meeting/participate/id/dR1Wz7Eb. Please notify me if you need to meet over Zoom instead.
Abstract
Over the last two decades, researchers in operations management have increasingly leveraged laboratory experiments to identify key behavioral insights. These experiments inform behavioral theories of operations management, impacting domains including inventory, supply chain management, queuing, forecasting, and sourcing. Yet, until now, the replicability of most behavioral insights from these laboratory experiments has been untested. We remedy this with the first large-scale replication study in operations management. With the input of the wider operations management community, we identify 10 prominent experimental operations management papers published in Management Science, which span a variety of domains, to be the focus of our replication effort. For each paper, we conduct a high-powered replication study of the main results across multiple locations using original materials (when available and suitable). In addition, our study tests replicability in multiple modalities (in-person and online) due to laboratory closures during the COVID-19 pandemic. Our replication study contributes new knowledge about the robustness of several key behavioral theories in operations management and contributes more broadly to efforts in the operations management field to improve research transparency and reliability.
About the Presenter
Jordan Tong is the Wisconsin Naming Partners Professor and Professor in the Department of Operations and Information Management at the Wisconsin School of Business.
Professor Tong’s research primarily employs mathematical modeling and experimental methods to investigate questions in operations management, analytics, and behavioral science. His research focuses on examining how human cognitive limitations interact with broader system dynamics to inform operations design. He has published in journals such as Management Science, Operations Research, Psychological Science, Manufacturing & Service Operations Management, and Production and Operations Management. He is currently an Associate Editor at Management Science and a Senior Editor at Production & Operations Management.
Professor Tong has taught undergraduate and Master’s-level courses in Operations Management, Operations Analytics, Supply Chain Management, Modeling & Optimization for Business Analytics, and the Psychology of Business Analytics. He received his PhD in Operations Management from the Fuqua School of Business at Duke University and his BA in Mathematics from Pomona College.
MIT System Dynamics Seminar | Relative versus Absolute Aspirations
Please visit the MIT System Dynamics Seminars page for more information.
Attend the System Dynamics Seminar being held next Friday, September 29th from 12:30-2:00 pm EST in the Jay W. Forrester conference room, E62-450, or via Zoom: https://mit.zoom.us/j/98105285349 (Password: SDFA23). Our guest speaker will be Jerker Denrell (University of Warwick) presenting Relative versus Absolute Aspirations (see abstract and brief bio below, announcement attached). Lunch will be provided to those attending in person.
If you would also like to schedule a 30-minute 1:1 meeting with him before or after the seminar, please fill out the following Doodle poll by COB tomorrow, September 22nd and I will confirm times and location with a calendar invite: https://doodle.com/meeting/participate/id/eg2g48rd. Please notify me if you need to meet over Zoom instead.
Abstract
Aspirations impact when managers search for new alternatives. Therefore, their level and adjustment to environmental conditions have important performance consequences. Past research has shown that higher aspiration leads to higher performance unless the environment is turbulent. When conditions can change quickly, long periods of search may not pay off. Using a simple and analytically tractable model, we show that when aspirations are defined in relative terms (being better than others), we get the opposite result: higher aspirations lead to higher performance. These contrasting outcomes are the result of externalities generated by relative aspirations: improvements by one agent can leave others unsatisfied. Our findings have interesting implications for goal setting for individuals and populations.
About the Presenter
Jerker Denrell grew up in Sweden, studied management, economics, philosophy and also some mathematics. He wrote a dissertation on game theory at Stockholm School of Economics but was converted by James March to think about learning and decision-making from a more behavioural perspective. He started his career at Stockholm School of Economics, worked at Stanford Business School, University of Oxford, and is now at University of Warwick. Jerker’s research focuses on learning processes and their implications. Instead of examining whether biases exist in how people process information, he has examined how the sample of experiences available to people can lead to systematic biases in choices and judgment. He also has a keen interest in how randomness impacts our lives and fortunes and how stochastic processes can explain what appears as regularities.
MIT System Dynamics Seminar | Complex Contagions and the Hidden Influence of the Network Periphery
Please visit the MIT System Dynamics Seminars page for more information.
You are invited to attend the System Dynamics Seminar being held on Friday, April 21st from 12:30-2:00pm EST in the Jay W. Forrester conference room, E62-450, or via Zoom: https://mit.zoom.us/j/99908059742 (Password: SDSP23). Our guest speaker will be Douglas Guilbeault (Haas School of Business, UC Berkeley) presenting Complex Contagions and the Hidden Influence of the Network Periphery (see abstract and brief bio below, announcement attached). Lunch will be provided to those attending in person and a reminder email will be sent out closer to the date.
If you would also like to schedule a 30-minute 1:1 meeting with him before or after the seminar, please fill out the following Doodle poll by COB Tuesday, April 18th and I will confirm times and location with a calendar invite: https://doodle.com/meeting/participate/id/boZ0Rxja. Please notify me if you need to meet over Zoom instead.
Abstract
The standard measure of distance in social networks – average shortest path length – assumes a model of “simple” contagion, in which people only need exposure to influence from one peer to adopt the contagion. However, many social phenomena are “complex” contagions, for which people need exposure to multiple peers before they adopt. In this talk, I argue that the classical measure of path length fails to define network connectedness and node centrality for complex contagions. I provide theoretical and empirical evidence that centrality measures and seeding strategies based on the classical definition of path length frequently misidentify the network features that are most effective for spreading complex contagions. To address these issues, I introduce novel measures of complex path length and complex centrality, which significantly improve the capacity to identify the network structures and central individuals best suited for spreading complex contagions. I validate this theory using empirical data on the spread of a microfinance program in 43 rural Indian villages. Implications for human cultural evolution are discussed.
About the Presenter
Douglas Guilbeault is an Assistant Professor in the Management of Organizations Group at the Haas School of Business. He studies how communication networks underlie the creation and diffusion of cultural content, such as linguistic categories and social norms. This investigation extends to how communication dynamics are shaped by various sources of influence, such as organizational culture and social media. His work has appeared in a number of top journals, including Nature Communications, The Proceedings of the National Academy of the Sciences, and Management Science, as well as in popular news outlets, such as The Atlantic, Wired, and The Harvard Business Review. Guilbeault’s work has received top research awards from The International Conference on Computational Social Science, The Cognitive Science Society, and The International Communication Association. He is co-director of the Berkeley-Stanford Computational Culture Lab, and he is a faculty affiliate of the Berkeley Institute for Data Science. He received his Ph.D. from the University of Pennsylvania, where he trained with sociologist Damon Centola in the Network Dynamics Group.
MIT System Dynamics Seminar | First Look at ReThink Health’s Multisolving Investment Model, Part II
Please visit the MIT System Dynamics Seminars page for more information.
You are invited to attend the System Dynamics Seminar being held on Friday, March 10th from 12:30-2:00pm EST in the Jay W. Forrester conference room, E62-450, or via Zoom: https://rippel-org.zoom.us/j/86004993630 (Passcode: 767250)*. Our guest speakers will once again be Jack Homer, Bobby Milstein, and Chris Soderquist (ReThink Health) presenting First Look at ReThink Health’s Multisolving Investment Model, Part II. Lunch will be provided to those attending in person.
*Please note that we are using a different Zoom link for this seminar
Abstract
Picking up where the Thriving Together Theater leaves off, this session will offer a first look at ReThink Health’s next-generation simulation tool, which we call a Multisolving Investment Model. This new tool will help stewards see for themselves WHY certain investments are especially powerful multisolvers in our quest to thrive together (such as efforts to establish racial fairness as a matter of system design; expand belonging and civic muscle; and secure the other vital conditions). As far as we know, this is the first dynamic model to track population-level changes in well-being separately by race/ethnicity, which in turn lets planners see how everyone benefits we invest more among those who have the most to gain.
During this “First Look” session, we will share (1) the origin story of this new model; (2) design features of a working prototype including a dynamic hypothesis, empirical sources, and calibration; as well as (3) insights from initial tests, including illustrative investment scenarios, optimization, and sensitivity to uncertainties. Together, we will discuss ideas for potential use-cases and facilitation options. But this session will largely concentrate on early insights from the new prototype model.
Technical Background: The new Multisolving Investment Model uses the vital conditions framework and builds upon two prior simulation models built to study investment scenarios. Here are background references about those three elements.
- Milstein B, Payne B, Kelleher C, Homer J, et.al. Organizing Around Vital Conditions Moves the Social Determinants Agenda into Wider Action.
Health Affairs Forefront. 2023; Feb 2. https://tiny.cc/VitalConditionsHA - Milstein B, Homer J, Soderquist C. How Can a Community Pursue Equitable Health and Well-Being after a Severe Shock? Ideas from an Exploratory Simulation Model. Systems. 2022;10(5):158. https://www.mdpi.com/2079-8954/10/5/158 (see also this self-guided online interface)
- Milstein B, Homer J. Which Priorities for Health and Well-Being Stand Out After Accounting for Tangled Threats and Costs? Simulating Potential Intervention Portfolios in Large Urban Counties. The Milbank Quarterly. 2020 February 6:1-27. https://onlinelibrary.wiley.com/doi/abs/10.1111/1468-0009.12448
Please visit https://sloangroups.mit.edu/saas/home/ for more information on all of the Academic Areas research seminars happening this semester.
MIT System Dynamics Seminar | A Replication Study of Operations Management Experiments in Management Science
Please visit the MIT System Dynamics Seminars page for more information.
You are invited to attend the System Dynamics Seminar on Friday, October 7th from 12:30-2:00pm EDT in the Jay W. Forrester conference room, E62-450, or via Zoom: https://mit.zoom.us/j/97141505370 (Password: SDFall2022). Our guest speaker will be Kyle Hyndman (University of Texas at Dallas) presenting A Replication Study of Operations Management Experiments in Management Science (see abstract and brief bio below, announcement attached). Lunch will be provided to those attending in person.
If you would also like to schedule a 30-minute 1:1 meeting with Kyle Hyndman, please fill out the following Doodle poll by COB Wednesday and I will confirm times with a calendar invite: https://doodle.com/meeting/participate/id/eE9E20me.
Abstract
Over the past two decades, researchers in operations management have increasingly leveraged laboratory experiments to identify key behavioral insights. These experiments inform behavioral theories of operations management, impacting domains including inventory, supply chain management, queuing, forecasting, and sourcing. Yet, until now, the replicability of most behavioral insights from these laboratory experiments has been untested. We remedy this with the first large-scale replication study in operations management. With the input of the wider operations management community, we identify ten prominent experimental operations management papers published in Management Science, which span a variety of domains, to be the focus of our replication effort. For each paper, we conduct a high-powered replication study of the main results across multiple locations using original materials. In addition, our study tests replicability in multiple modalities (in-person and online) due to laboratory closures during the COVID-19 pandemic. Our replication study contributes new knowledge about the robustness of several key behavioral theories in operations management and contributes more broadly to efforts in the operations management field to improve research transparency and reliability.
Kyle Hyndman is a Professor of Managerial Economics at the University of Texas at Dallas. He studies problems related to (i) strategic learning, (ii) coordinating behavior, and (iii) bargaining and coalition formation using both theory and experiments to provide insights on these problems. He works on problems of interest to both economists and operations managers and his research has been published in leading journals in both economics and operations management. Most recently, he has co-edited the book “Bargaining: Current Research and Future Directions”, with the aim of providing scholars an up-to-date snapshot of the literature on bargaining theory, experiments and empirics as well as promising new directions for the field.
MIT System Dynamics Seminar | Simpler is (Sometimes) Better: A Comparison of Cost Reducing Agent Architectures in a Simulated Behaviorally-Driven Multi-Echelon Supply Chain
Please visit the MIT System Dynamics Seminars page for more information.
You are invited to attend the System Dynamics Seminar being held this Friday from 12:00-1:30 pm ET in the Jay W. Forrester conference room, E62-450, or via Zoom:: https://mit.zoom.us/j/97116456932 (password: SDFall2022).
Our guest speaker will be James Paine (MIT Sloan) presenting Simpler is (Sometimes) Better: A Comparison of Cost Reducing Agent Architectures in a Simulated Behaviorally-Driven Multi-Echelon Supply Chain Lunch will be provided to those attending in person.
If you would also like to schedule a 30-minute 1:1 meeting with Brent Moritz, please fill out this Doodle poll https://doodle.com/meeting/participate/id/b2vWmxAb by COB Wednesday and I will confirm times with a calendar invite.
Please check here for the latest updates on MIT’s COVID policies: https://now.mit.edu/policies/
Abstract
Supply chains partially consist of, and almost exclusively exist for, people. Behavioral Operations Management has endeavored to identify how the behavioral responses of these people, decision makers in supply chains, differ from the fully rational and to identify policies incorporating on these differences. The complexity of such policies, and the underlying assumptions of rationality, can vary widely. This work utilizes a model of a multi-echelon supply chain, captured by the classic Beer Game inventory management simulation, to compare the features of policies that can reduce costs from bullwhip when placed in such a system while still allowing other entities to behave in a behaviorally. This work contributes to existing supply chain management literature by applying a dueling-DQN structure and Model-Predictive learning structure to this multi-echelon supply chain system in a manner that can be leveraged for other research. However, this is secondary to the main observation of this work that relatively simple ordering policies, including static base-stock rules, in these behaviorally-driven systems can have large cost-reducing effects only marginally behind more complex methods. Additionally, for model-predictive learning agents, even myopic approaches with limited information about the overall system and greedy objectives can be cost reducing globally. This has direct managerial implications by showing how a decision maker embedded in a supply chain with other behavioral actors does not need to be perfectly rational and can be locally focused while achieving global benefits.
James Paine is a fifth-year doctoral candidate at the Sloan School of Management at MIT, studying System Dynamics and its applications to product and service delivery systems. Prior to coming to the System Dynamics group, James gained experience in the nuclear, reverse logistics, and consumer apparel industries, as both an engineer and product lifecycle-focused marketer. Currently, James focuses on behavioral operations management questions, including human-algorithm interactions, supply chain research and analytics, and dynamic modeling of product and service delivery systems. More information about James and his research can be found at https://jpaine.info/.
MIT System Dynamics Seminar | Unraveling Behavioral Ordering: Relative Costs and the Bullwhip Effect
Please visit the MIT System Dynamics Seminars page for more information.
You are invited to attend the System Dynamics Seminar being held this Friday from 12:00-1:30pm ET in the Jay W. Forrester conference room, E62-450, or via Zoom: https://mit.zoom.us/j/96947695163 (Password: SDFall2002).
Our guest speaker will be Brent Moritz (Penn State University) presenting Unraveling Behavioral Ordering: Relative Costs and the Bullwhip Effect (see abstract and brief bio below). Lunch will be provided to those attending in person.
If you would also like to schedule a 30-minute 1:1 meeting with Brent Moritz, please fill out this Doodle poll https://doodle.com/meeting/participate/id/b2vWmxAb by COB Wednesday and I will confirm times with a calendar invite.
Please check here for the latest updates on MIT’s COVID policies: https://now.mit.edu/policies/
Abstract
Behavioral ordering results in poorer supply chain performance. However, how might one separate and evaluate the behavioral causes of increased orders from the effect of increased orders elsewhere in the supply chain? In this paper, we investigate several related questions: (i) What is the impact of behavioral ordering in a multi-echelon supply chain? Although prior literature has shown that behavioral ordering is detrimental to performance, we show how much worse it is than rational ordering. (ii) How does behavioral ordering in one echelon impact the costs elsewhere in the supply chain? Answering this question is not straightforward, as it requires separating the impact of a rational response to incoming orders (such as increasing safety stock) from additional behavioral ordering. (iii) Does the cognitive reflection level of each decision maker impact costs in heterogeneous supply chains? (iv) What is the impact of having more than one behavioral decision maker in a supply chain? We provide evidence to show the impact of adding additional behavioral decision-makers to a supply chain. We also investigated if human behavior is consistent with a policy of dynamic updating of inventory, such as changing the amount of safety stock in response to changes in incoming demand.
We use data from a laboratory experiment, estimate behavioral parameters, and use a simulation to evaluate the cost impact of bullwhip behavior on the supply chain and by echelon. Unsurprisingly, behavioral ordering anywhere in the supply chain increases cost. However, these costs are not shared equally: Behavioral ordering by a retailer results in a larger relative cost increase elsewhere in the supply chain. In contrast, behavioral ordering by a wholesaler or distributor tends to increase the cost within that echelon. Individual decision-makers with high cognitive reflection tend to have lower costs for their supply chain, and these individuals also have lower costs for their individual echelons. We also provide initial evidence regarding the cost of multiple human decision makers in a supply chain. Adding additional behavioral decision makers increases cost, though the cost increases show a diminishing return to scale.
Brent Moritz is an Associate Professor of Supply Chain Management at the Smeal College of Business at Pennsylvania State University. He is a faculty affiliate of the Laboratory for Economics, Management and Auctions (LEMA) and is Co‐Director of Research for the Center for Supply Chain Research (CSCR) at Penn State. He earned his PhD (Operations and Management Science) at the Carlson School of Management at the University of Minnesota. He also holds a BS in Mechanical Engineering from Valparaiso University and an MBA from the Weatherhead School of Management at Case Western Reserve University. Prior to obtaining his PhD, he held positions in manufacturing operations and supply chain management at BorgWarner, Eaton and Parker Hannifin. This included international experience working in Mexico, England and Germany.
Dr. Moritz has research interests including supply chain management, behavioral operations, risk management and cognitive decision processes. His research is focused on decision‐making in contexts such as inventory, forecasting and supplier selection. His research has been published in Management Science, Journal of Operations Management, Decision Sciences Journal, Manufacturing and Service Operations Management, and Production and Operations Management. For further information: https://directory.smeal.psu.edu/bbm3
MIT System Dynamics Seminar | Dynamics of American Firms: Data and a Family of Models
Please visit the MIT System Dynamics Seminars page for more information.
You are invited to attend the System Dynamics Seminar being held this Friday, February 25th from 1:00-2:30 pm ET in the Jay W. Forrester conference room, E62-450, or via Zoom: https://mit.zoom.us/j/94333057556 (Password: SDSpr22). Our guest speaker will be Robert Axtell (George Mason University) presenting Dynamics of American Firms: Data and a Family of Models (see abstract and brief bio below). A reminder will be sent out closer to the date.
Please check here for the latest updates on MIT’s indoor eating and drinking policies: https://now.mit.edu/policies/events/
Abstract: Using data on the population of all American firms having employees over the last 40 years, several dozen gross empirical regularities, uncovered with statistical and machine learning techniques, will be described. These have to do with firm sizes, ages, growth rates, productivities, financial attributes, inter-firm networks, and spatial locations and involve 100s of millions of workers and 10s of millions of firms. A family of models based on a team production specification will be shown to be capable of reproducing many of these patterns. The equilibria and stability of the model are characterized. Computational challenges associated with rending this model at full-scale with the U.S. economy—in any period, 120 million worker agents self-organized into 6 million emergent firms—will be discussed. This talk is based on a forthcoming book.
Rob Axtell is Professor of Computational Social Science at George Mason University, Co-Director of the Computational Public Policy Lab at the Schar School of Policy and Government at Mason, and an affiliate of the Department of Economics there. His research focuses on the application of computational modeling and simulation techniques to economics and finance. He is External Faculty Fellow at the Santa Fe Institute and Visiting Researcher at Google. He is currently on sabbatical at MIT Sloan.
Professor Axtell is the author, with Joshua Epstein, of Growing Artificial Societies: Social Science from the Bottom Up (MIT Press). His research has appeared in Science, Nature, Proceedings of the National Academy of Sciences, as well as in leading field-specific journals such as The American Economic Review, and has been reprised in newspapers (e.g., Wall St. Journal, Los Angeles Times, Washington Post) and science magazines (e.g., Scientific American, Technology Review, Wired). For the past decade he has been using micro-data on individuals to build large-scale models of the Financial Crisis of 2008-9 (with JD Farmer, Oxford, and J Geanakoplos, Yale), the dynamics of business firms (with O Guerrero, Turing Institute), and natural resource exploitation, e.g., fisheries (with UC Santa Barbara, Oxford, and the Ocean Conservancy). The research on companies is described at length in a forthcoming book, Dynamics of Firms from the Bottom Up Data, Theories, and Models, due out later this year, which uses U.S. micro-data on firm sizes, ages, growth rates, networks, and locations to create a model at 1:1 scale with the American economy.