Publications / Journal Articles

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 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. 

Featured 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 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 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] Operations Research, major revision (2022).

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. 

We study the impact of cannabis legalization on operational metrics using data from different areas of the US. 

Abstract: Many US states have legalized recreational cannabis in the last decade. Using a difference-in-differences approach, we investigate the effect of recreational cannabis legalization (RCL) on hospital operations. We find that legalization alters the workload of hospital staff by changing the patient mix: While there is a null effect on total inpatient admissions, more cannabis-related patients are admitted, who, in turn, increase workload complexity. More strikingly, hospitals speed up care for other (i.e., non-cannabis) patients, with legalization lowering lengths of stay by 2.6%. We attribute this phenomenon to cannabis generating workload for hospital staff that reduces the resources (including staff time) available to other patients. We further find adverse effects on experiential quality of care and medical professionals' compliance: First, patient satisfaction with hospital noise levels at night, hospital staff helpfulness, and information received about home recovery significantly decrease, resulting in lower experiential quality of care and potential financial damages for providers. Second, disciplinary actions against doctors and nurses increase by about 34%. These findings inform hospital managers about what to expect after legalization and offer evidence of another dimension—the impact on hospitals—that governments should consider when deciding on legalization. 

"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 at Management Science. [Full manuscript available upon request.]

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. 

"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. Preparing for submission to Management Science in Q1 2023.

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").

"Working Smarter: The Effects of Performance Pay on Discretionary Task Sequence, Learning, and Performance."

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 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. 

Which tasks are prioritized to be completed the next is a key driver of operational performance. Yet, these decisions are often in the hands of those executing the tasks. With technologies increasingly facilitating real-time feedback, we propose that managers can use such feedback to influence workers' decisions. 

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 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.