Publications / Journal Articles
Engel, Josh, Tyler A. Jacobson, Michael Markl, Bradley D Allen, and Maria Ibanez. "Operational Costs of 4D Flow MRI: A Break-Even Analysis." J Cardiovasc Magn Reson. 2025 Jun 25:101928. doi: 10.1016/j.jocmr.2025.101928. Epub ahead of print. PMID: 40578562.
This study evaluates the financial barriers to adopting 4D Flow MRI (4DF), an advanced technology with proven clinical benefits in cardiovascular care but limited use outside academic centers. Each 4DF scan adds about $101 in costs, and at current reimbursement levels, hospitals would need roughly 112–778 annual scans to break even, depending on software costs, scan time, and reimbursement rate. Faster imaging techniques reduce this threshold by nearly half. The findings show that long scan times and low reimbursement make 4DF viable only in high-volume centers today. Broader adoption will require accelerated imaging technology and improved reimbursement policies to make 4DF financially viable.
Ibanez, Maria R., and Michael W. Toffel. 2020. "How Scheduling Can Bias Quality Assessment: Evidence from Food Safety Inspections." Management Science 66:6, 2396-2416. (Working paper version available here.)
Abstract: Accuracy and consistency are critical for inspections to be an effective, fair, and useful tool for assessing risks, quality, and suppliers—and for making decisions based on those assessments. We examine how inspector schedules could introduce bias that erodes inspection quality by altering inspector stringency. Our analysis of thousands of food-safety inspections reveals that inspectors are affected by the inspection outcomes at their prior-inspected establishment (outcome effects), citing more violations after they inspect establishments that exhibited worse compliance levels or trends. Moreover, consistent with negativity bias, the effect is stronger after observing compliance deterioration than improvement. Inspection results are also affected by when the inspection occurs within an inspector’s day (daily schedule effects): Inspectors cite fewer violations after spending more time conducting inspections throughout the day and when inspections risk prolonging their typical workday. Overall, our findings suggest that currently unreported violations would be cited if the outcome effects—which increase scrutiny—were triggered more often and if the daily schedule effects—which erode scrutiny—were reduced. For example, our estimates indicate that if outcome effects were doubled and daily schedule effects were fully mitigated, 11% more violations would be detected, enabling remedial actions that could substantially reduce foodborne illnesses and hospitalizations. Understanding and addressing these inspection biases can help managers and policymakers improve not only food safety but also process quality, environmental practices, occupational safety, and working conditions.
Featured in HBR, Forbes, Food Safety Magazine, Food Safety News, The New Food Economy, and Kellogg Insight.
Highlighted in INFORMS Analytics Collections (Vol. 9: Feeding the World through Analytics).
Ibanez, Maria R., and Bradley R. Staats. 2019. "Field Experiments in Operations Management." Operations Research & Management Science in the Age of Analytics. In INFORMS TutORials in Operations Research. October 2019, 1-16.
Abstract: Field experiments are controlled interventions in the real world that enable researchers to measure the effects of a treatment on a randomly assigned subset of subjects. In this paper, we review the advantages and disadvantages of field experiments and provide some practical prescriptions to attain and evaluate a field experiment’s relevance—in other words, the theoretical implications of understanding the effects of the treatment—and rigor, based on many methodological considerations.
Ibanez, Maria R., Jonathan R. Clark, Robert S. Huckman, and Bradley R. Staats. 2018. "Discretionary Task Ordering: Queue Management in Radiological Services." Management Science 64(9): 4389-4407. (Working paper version available here.)
Abstract: Work scheduling research typically prescribes task sequences implemented by managers. Yet employees often have discretion to deviate from their prescribed sequence. Using data from 2.4 million radiological diagnoses, we find that doctors prioritize similar tasks (batching) and those tasks they expect to complete faster (shortest expected processing time). Moreover, they exercise more discretion as they accumulate experience. Exploiting random assignment of tasks to doctors’ queues, instrumental variable models reveal that these deviations erode productivity. This productivity decline lessens as doctors learn from experience. Prioritizing the shortest tasks is particularly detrimental to productivity. Actively grouping similar tasks also reduces productivity, in stark contrast to productivity gains from exogenous grouping, indicating deviation costs outweigh benefits from repetition. By analyzing task completion times, our work highlights the trade-offs between the time required to exercise discretion and the potential gains from doing so, which has implications for how discretion over scheduling should be delegated.
Featured in Forbes, Inc., Inman, Quick Base, and Quartz.
Ibanez, Maria R., and Anthony Pennington-Cross. 2013. "Commercial Property Rent Dynamics in U.S. Metropolitan Areas: An Examination of Office, Industrial, Flex and Retail Space." Journal of Real Estate Finance and Economics 46, no. 2 (February 2013): 232–259. (Working paper version available here.)
Abstract: This paper is concerned with the market rental rate for space offered by commercial property and how that rental rate evolves over time. Rental rates reflect the value of the services provided by the property and can have a significant impact on the ability of its owners to make monthly debt obligations. We investigate commercial property rent dynamics for 34 large metropolitan areas in the U.S. The dynamics are studied from the second quarter of 1990 through the second quarter of 2009 and the results are compared across four property types or uses (office, industrial, flex, and retail). There is substantial heterogeneity in both the long and short run responses to changing demand and supply conditions. In general, the office market is the slowest to adjust back towards equilibrium while industrial and flex markets adjust back to the long run equilibrium very quickly. For industrial and office types, the speed of adjustment is substantially faster within quality segments and is strongest for grade A properties.
Selected Working Papers / Work in Progress
"How Schedule Flexibility Affects Job Applications." [SSRN]
We often assume everyone wants schedule flexibility and there is research showing this flexibility is critical to gig workers. In contrast, however, a study asking applicants to a telephone interviewer position about their preferences found that, on average, they did not value flexible schedules. Analyzing a variety of jobs across positions and across companies, this study reconciles these different results and identifies factors that explain when flexibility is more valued. The findings provide insights to employers worried about the Great Resignation and incomplete discussions about what workers want.
Featured in The Economist. Mint.
"Impact of Cannabis Legalization on Hospital Overcrowding, Performance, and Health Indicators." [SSRN] With Maksim Yakovlev.
Cannabis is the most common federally illegal drug in the United States. The federal stance contrasts with the growing trend of recreational cannabis legalization (RCL) across states. A vital implementation question is how legalization affects hospitals. We propose that as cannabis spreads throughout society, its effects permeate healthcare systems, reaching inpatient wards. Cannabis peculiar symptoms—including aggravated chronic conditions, psychosis, agitation, and intractable vomiting—will increase workload complexity, restrict staff time and hospital capital resources available to other patients, and cause disturbance. To unpack these effects, we study how RCL influences hospital operations across three dimensions: length of stay, experiential quality of care, and medical providers’ behaviors.
Using a difference-in-differences approach, we find that hospitals speed up care, with legalization shortening inpatient lengths of stay by 2.6%. Second, patient satisfaction with hospital noise levels at night, staff helpfulness, and information received about home recovery decrease by 5-10%, with potential reputational and financial damages for hospitals. Third, disciplinary actions against doctors, physician assistants, and nurses increase by 34%.
These findings underscore the need for policymakers to consider the broader implications of RCL, including its impact on hospital operations, amidst shifting societal norms. Strategies to mitigate the adverse effects of RCL should be explored, focusing on maintaining quality care. By understanding and addressing the challenges posed by RCL, healthcare providers can adapt their practices to ensure optimal patient care in an evolving regulatory landscape.
"Second-Party vs. Third-party Audits: Evidence from Global Supply Chain Monitoring." [SSRN] With Ashley Palmarozzo, Jodi L. Short, and Michael W. Toffel. Under review.
Many global buyers are shifting from their own ("second-party") auditors to relying more heavily on hired ("third-party") auditors to monitor and prevent environmental and social misconduct at their suppliers' factories. However, some brands are concerned that this trend risks eroding audit quality. Using data from one of the world's largest fashion brands, this project evaluates the performance of in-house second-party and third-party auditors and investigates the allocation (scheduling) of different auditors to factories across geographies over time.
Contrary to expectations, the analysis reveals that third-party auditors are significantly less effective—particularly in regions with higher corruption or weaker internal oversight. These findings challenge prevailing assumptions about audit independence and underscore the importance of context-sensitive governance mechanisms. This research offers concrete insights into international regulatory frameworks and multilateral efforts to promote responsible sourcing and accountability.
Key findings:
• In-house ("second-party") audits yield more violations per audit, holding everything else constant, including the factory being audited and the year and sequence of the audit. (All audits follow the same methods and are assigned to suppliers quasi-randomly.) Although this result may vary across settings, it demonstrates that internal audits can be superior to external ones, as evidenced by this major international buyer. This challenges the assumption that third-party-verified audits are superior, suggesting that regulations requiring them could backfire.
• Gap closes in regions with a higher % of audits done in-house (oversight).
• Gap widens in regions with more corruption.
"Under-Promising and Over-Delivering to Improve Patient Satisfaction at Emergency Departments: Evidence from a Field Experiment Providing Wait Information." [SSRN] With Sina Ansari, Laurens G. Debo, Seyed M.R. Iravani, and Sanjeev Malik, MD.
We conduct a field experiment at an urban ED to investigate whether and how managers could improve patient satisfaction by communicating waits to patients.
Featured in FT Newsletter ("How to boost patient satisfaction").
"The Effects of Mandated and Discretionary Mobile App Updates." [Full manuscript available upon request.] With Alejandro Hernandez.
Mobile app developers must decide when and how to update their products, yet platforms such as Google Play and Apple's App Store frequently impose mandatory updates to maintain ecosystem compatibility. Failure to comply can reduce app visibility and revenue potential, constraining developer discretion. Using a large-scale clickstream dataset comprising over one million users from a freemium mobile application, we investigate the impact of mandated and discretionary updates on user retention and engagement. We find that discretionary updates—those initiated by developers, presumably to enhance features or usability—enhance retention and ad views (a measure of engagement, and the app's main revenue source). In contrast, mandated updates increase churn and do not translate into measurable engagement gains, consistent with their imposition of user inconvenience—such as requiring app restarts, reauthentication, login disruptions, or altered privacy controls—without delivering visible improvements. Batched updates that combine mandated requirements with user-facing features mitigate some negative effects, though they can still elevate churn risk. Our study contributes to information systems research by providing the first systematic comparison of mandated and discretionary updates on the behavior of existing users. We extend theories of digital continuance and platform governance by bringing a value-inconvenience mechanism: when update benefits are visible and intuitive, users remain; when benefits are opaque or compliance-driven, churn increases. These findings provide actionable guidance for developers and platforms on update timing, batching strategies, and communication practices that strike a balance between compliance and user experience.
"Back-End Changes, Front-End Behavior: The Effects of Ad Mediation." With Alejandro Hernandez.
Many mobile applications, particularly those operating under freemium models, rely on rewarded video ads to generate revenue. Despite the widespread use of ad mediation platforms like Google AdMob to integrate multiple ad networks and optimize monetization, ad delivery failures remain a common issue. These failures often arise from mismatches in supply and demand, unsupported ad formats, or low advertiser interest in certain user segments, resulting in reduced user engagement and ads watched. This paper examines how incorporating additional ad networks affects ad availability and user engagement.
"Working Smarter: The Effects of Performance Pay on Discretionary Task Sequence, Learning, and Performance." [Full manuscript available upon request.]
We investigate the exercise of discretion under pay-for-performance using data from radiologists working across the US.
"Impatient or Selective? Estimation of Customers' Scheduling Preferences in Attended Home Delivery." [SSRN] With Pol Boada-Collado, Sunil Chopra, and Karen Smilowitz.
Understanding customers’ sensibility to delivery lead time can allow retailers to balance customer satisfaction and shipping costs in attended home delivery. We take an econometric approach to explore how retailers should incorporate customer preferences in the scheduling of their attended home delivery. Using transactional data from a major furniture company, we find that the speed of delivery is of limited importance relative to other priorities when customers choose their preferred delivery date.
"Managing Discretion: How Real-time Feedback Influences Workers' Easy Task Selection." With Farah Arshad and Bart Dierynck. [Full manuscript available upon request.]
Which tasks are prioritized to be completed next is a key driver of operational performance. Yet, these decisions are often in the hands of those executing the tasks. As technologies increasingly facilitate real-time feedback, we propose that managers can use such feedback to influence workers' decisions.
"Disparity in Maternal Care and Operational Factors: Role of Specialization, Exposure, and Ownership in Eliminating the Gap." [Full manuscript available upon request.] With Maksim Yakovlev.
Managerial Articles
Ibanez, Maria R., and Michael W. Toffel. "To Improve Food Inspections, Change the Way They’re Scheduled." Harvard Business Review (website, May 16, 2019).
Executive Summary: Food-borne illness affects an estimated 48 million Americans every year resulting in 3,000 deaths and the hospitalization of 128,000 people, according to the Centers for Disease Control and Prevention (CDC). Beyond that, foodborne illness in the U.S. is enormously costly, with an estimated collective annual bill of $55 billion in medical treatment, lost productivity and lost wages, not to mention litigation expenses. Given this immense impact, we embarked on a research project to try to find ways to improve how local government inspectors handle their daunting task of ensuring that restaurants, hospitals, schools, and supermarkets prepare food safely. These inspections are conducted in much the same way as they have been for decades. The research suggests that they should focus on more thoughtful scheduling as a way to improve outcomes.
Featured in GoLocalProv.
Cotteleer, Mark, Maria R. Ibanez, and Geri Gibbons. "The Answer is 9,142: Understanding the Influence of Disruption Risk on Inventory Decision Making." Deloitte Review 14 (January 2014).
Executive Summary: We conducted a field experiment to understand how inventory managers modify their decisions in response to potential disruptions in supply. Our study involved 81 experienced supply chain managers and 41 students majoring in supply chain management at a program ranked among the top 15 in the United States. The results are not encouraging: Virtually everyone (99.7 percent of subjects) responded suboptimally, overreacting to low probabilities of disruption and underreacting to high probabilities. With inventory planning being critical to customer service and to overall company performance, the implications of our results should be worrying to leaders of US companies that, as of July 2013, held approximately $1.7 trillion in inventory.
Book Chapters
Ibanez, Maria R., and Bradley R. Staats. "Behavioral Empirics and Field Experiments." In The Handbook of Behavioral Operations, edited by Karen Donohue, Elena Katok, and Stephen Leider. New York, NY: John Wiley & Sons (September 2018). (Working paper version available here.)
Summary: As the study of behavioral operations continues to grow, an increasing number of researchers are turning to the field (e.g. conducting observational studies or natural or field experiments) to push deeper in order to find the answers to relevant behavioral questions. Field data can bring richness to any study seeking to explain real-world phenomena and can complement lab experiments. This not only creates the potential for additional insight but also helps to overcome methodological challenges (while at the same time adding new challenges). By turning to the field, it is possible to expand the scope of behavioral operations management such that it continues to build theory that is both rigorous and relevant. Altogether we hope this chapter would aid behavioral operations management scholars in utilizing a variety of empirical approaches to conduct research that utilizes field data to advance scholarship and practice.
