Is there a Principal-Agent problem between large retail-chain pharmacy corporations and community pharmacists?

Is there a Principal-Agent problem between large retail-chain pharmacy corporations and community pharmacists?

 

Date: 31 October 2025

 

(This is part of a working paper. Updates are expected.)

 

The principal-agent problem is a type of market failure involving a misalignment of incentives between the owners of a company or firm (principals) and the employees that they hire (agents).[1] The conflict arises when the agents (or employees) do not act in accordance with the interest or expectation of the principals (firm). Principals delegate the agents to represent their interest, oftentimes providing them with decision-making capabilities. However, the principals cannot control the agents, nor do they have the same level of information as the agents (asymmetric information). This conflict can lead to non-Pareto optimal conditions, which would result in inefficiency and harm to both the principals and agents.

Misalignment of incentives is a central issue between large retail-chain pharmacy corporations and community pharmacists. Using the principal-agent problem framework, large retail-chain pharmacies (principals) hire community pharmacists (agents) to represent their interest to maximize their shareholder value (e.g., increased profits). However, community pharmacists are not interested in maximizing profits for the large retail-chain pharmacy corporations. Rather, they are interested in providing high-quality care to their patients and community, which is in direct conflict with the expectations of the large retail-chain pharmacy corporations. This misalignment of interests between the large retail-chain pharmacy corporations and community pharmacists has been responsible for unsafe working conditions, increased medication errors, pharmacist burnout and retention issues, and corporate bankruptcy.

This article will attempt to establish the misalignment between the large retail-chain pharmacy corporations and community pharmacists and offer some recommendations to address this principal-agent problem.

 

Misalignment of Incentives

A substantial number of licensed pharmacists work in the community pharmacy setting, which includes independent pharmacies, small and large retail chain pharmacies, supermarkets, mass merchandizers, and health-system retail pharmacies. In a 2024 work survey of pharmacists in the United States (US), 59.1% of pharmacists were working in the community setting, and, among those, 22.4% were working in large chain pharmacies.[2]

Large-chain retail pharmacy corporate leaderships are focused on maximizing shareholder value and downplaying the professional and ethical responsibilities of the pharmacist working in the community setting. Community pharmacists, on the other hand, often are not interested in these corporate incentives (e.g., increased earnings per share) and are focused on upholding their professional and ethical responsibilities to providing the highest quality care to their patients and community. Large retail chain pharmacy corporations expect their pharmacists to not only perform their duties as community pharmacists but also expect them to meet productivity performance measures such as filling and dispensing quotas. According to the California Code, Business and Professions Code,  a “quota” is defined as a fixed number or formula related to prescriptions filled, services rendered to patients, programs offered to patients, and revenue obtained as a means to evaluate or measure the performance of the pharmacy staff.[3] This practice of using quotas to evaluate the productivity performance of community pharmacists has resulted in unsafe working conditions, increased medication errors, and increased burnout and retention issues.[4] According to a 2020 survey conducted among community pharmacist in Ohio, 82% of respondents reported either “agreed” or “strongly agreed” with the statement, “I feel pressure by my employer or supervisor to meet standards or metrics that may interfere with safe patient care.”[5]

The burden of meeting productivity performance-based measures such as prescription quotas contribute to an unsafe work environment where medication errors can occur. Compound this with an increased workload and lack of proper staffing and resources, and the conditions for a serious medication error increase the probability of a serious event. In a 2024 workload report, 91% of pharmacists working at chain pharmacies reported having “high” or “excessively high” workload compared to 55% of pharmacists working at independent pharmacies.[2] Similar findings were reported in 2019, suggesting that this practice and culture has been normalized for many years. Additionally, 54.9% of community pharmacists responded that they “disagreed” or “strongly disagreed” with the statement that “My organization is willing to extend resources to help me perform my job to the best of my ability,” and 56.3% of community pharmacists reported that they “disagreed” or “strongly disagreed” with the statement, “My organization is committed to employee health and well-being.”

Another factor that complicates the principal-agent problem is the involvement of the pharmacy benefits management (PBM) that do not provide pharmacies with enough compensation for filling prescriptions.[6] The reimbursement rate for each prescription fill is often less than the cost of supply (e.g., label and bottle), which means that the community pharmacies are losing revenue with each fill. This has dangerous consequences as the large, chain retail pharmacy corporations will try to maximize profits by imposing unreasonable prescription fill quotas and decreasing staffing levels, thereby creating an unsafe work environment and causing pharmacist burnout.[7,8] Moreover, the lack of proper reimbursements for prescription fills has led to many pharmacies closing their doors. According Guadamuz and colleagues, 29.4% of pharmacies that were opened between 2010-2020 closed their doors in 2021.[9] Further, Rite-Aid, one of the largest retail-chain pharmacies in the US filed for bankruptcy in October 2025, partly due to poor reimbursements from PBMs.[10]

 

Recommendations

Given the market failure associated with this principal-agent problem, governmental action in the form of legal policy may be needed. For instance, California passed a law prohibiting chain community pharmacies from using quotas to measure the performance of pharmacy staff to address the concerns of rising medication errors due to unsafe work environments in 2021.[3,11] Shortly afterwards in October 2022, Walgreens, one of the largest retail-chain pharmacies in the US announced that they would abandon the use of quotas for productivity performance-based evaluations of pharmacy staff.[12] However, these changes have not eliminated the use of these productivity performance-based metrics, and misaligned incentives between large retail-chain pharmacy corporations and community pharmacists have continued to result in unsafe environments, increased medication errors, and increased burnout and retention issues. 

To address unsafe working conditions due to understaffing and resulting in increased medication errors, California Governor Gavin Newsom signed into law the “Stop Dangerous Pharmacies Act” (AB 1286) in 2024.[13] This bill, the first of its kind, requires large retail-chain pharmacies to staff their pharmacies with at least one pharmacy technician or clerk to assist with pharmacy-related services and to report all medication errors. Although current California law requires that pharmacies include a pharmacy staff to assist the pharmacist, this had not been enforced. The new bill will empower pharmacists to make staffing decisions instead of the large retail-chain pharmacy corporations thereby improving working conditions and reducing medication errors.   

In October 2025, California Governor Gavin Newsom signed into law Senate Bill 41 (SB-41) that impose upon pharmacy benefits managements (PBMs) a fiduciary duty to their clients, ban spread pricing (profiting from the difference in costs between health plans and pharmacies), and providing fair reimbursement to pharmacies.[14] This bill has important implications for pharmacies by improving their reimbursement rates for each prescription filled thereby allowing for improved a profit margin. For community pharmacists, this could lead to reduced burden from the large retail-chain pharmacy corporations to increase revenue through unreasonable prescription fill quotas. However, future evaluation will need to assess the effectiveness of this policy on the principal-agent problem between large retail-chain pharmacies and community pharmacists.   

 

Conclusions

In this brief article about the principal-agent problem between large retail-chain pharmacy corporations and pharmacists, I try to establish the framework for potential misaligned incentives leading to negative consequences. Pharmacists (agents) are delegated to represent the interests of the large retail-chain pharmacy corporations (principals), but their incentive to their professional oath and service to community are in direct conflict with the rent-seeking behaviors of large retail-chain pharmacy corporations. This conflict inevitably led to unsafe working conditions, increased medication errors, and increased burnout and retention issues. Recently legislation has been developed to address the issues of staffing, medication errors, and quotas to improve patient and community safety. However, the impact of these legal interventions has yet to be determined.

References

  1. Jensen MC, Meckling WH. Theory of the firm: Managerial behavior, agency costs and ownership structure. Journal of Financial Economics. 1976;3(4):305-360. doi:10.1016/0304-405X(76)90026-X

  2. Mott DA, Bakken BK, Nadi S, et al. Final Report of The 2024 National Pharmacist Workforce Survey. Pharmacy Workforce Center; 2024. https://www.aacp.org/article/national-pharmacist-workforce-studies

  3. California Code, Business and Professions Code - BPC § 4113.7.; 2023. Accessed October 31, 2025. https://codes.findlaw.com/ca/business-and-professions-code/bpc-sect-4113-7/

  4. O’Donnell J, Vogenberg FR. Imperatives for Oversight Of Professional Personnel. P T. 2015;40(11):744-774.

  5. Francis SG. Pharmacists’ Perceptions About the Effect of Work Environment Factors on Patient Safety in Large-Chain Retail Pharmacies. J Pharm Technol. 2022;38(6):376-378. doi:10.1177/87551225221116000

  6. Joyce G. The cost of misaligned incentives in the pharmaceutical supply chain. Health Aff Sch. 2025;3(7):qxaf126. doi:10.1093/haschl/qxaf126

  7. Mott D, Doucette W, Schommer J, Gaither CA. Opinion: Why your chain-store pharmacist is so unhappy. CNN. December 13, 2023. Accessed October 4, 2025. https://www.cnn.com/2023/12/13/opinions/pharmacy-working-conditions-mott-doucette-schommer-gaither

  8. Coz EL. Prescription for disaster: America’s broken pharmacy system in revolt over burnout and errors. USA TODAY. Accessed October 4, 2025. https://www.usatoday.com/story/news/investigations/2023/10/26/pharmacy-chains-dangerous-conditions-medication-errors/71153960007/

  9. Guadamuz JS, Alexander GC, Kanter GP, Qato DM. More US Pharmacies Closed Than Opened In 2018–21; Independent Pharmacies, Those In Black, Latinx Communities Most At Risk. Health Affairs. 2024;43(12):1703-1711. doi:10.1377/hlthaff.2024.00192

  10. Case Summary: Rite Aid Chapter 11. Bondoro. May 10, 2025. Accessed October 31, 2025. https://bondoro.com/rite-aid/

  11. SB 362- CHAPTERED. Accessed October 31, 2025. https://leginfo.legislature.ca.gov/faces/billTextClient.xhtml?bill_id=202120220SB362

  12. Kaplan A. Walgreens will stop judging its pharmacy staff by how fast they work. NBC News. October 28, 2022. Accessed October 31, 2025. https://www.nbcnews.com/health/health-care/walgreens-will-stop-judging-pharmacy-staff-fast-work-rcna54297

  13. Stop Dangerous Pharmacies Act is signed into California Law | Official Website - Assemblymember Matt Haney Representing the 17th California Assembly District. Accessed October 31, 2025. https://a17.asmdc.org/press-releases/20231009-stop-dangerous-pharmacies-act-signed-california-law

  14. California SB41 | 2025-2026 | Regular Session. LegiScan. Accessed October 31, 2025. https://legiscan.com/CA/bill/SB41/2025

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R - Tips and Tricks (Guide) - Part 2

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I wrote a second R guide to help students navigate and use R and RStudio in their biostatistics course. I focused on creating vectors, matrices, and dataframes.

The guide can be found on my RPubs site.

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Ratio of risk ratios in R

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I ran into a problem where I had two risk ratios, but I wanted to evaluate the statistical difference between them. I couldn’t find an R package, but I found a paper by Altman and Bland that go over the step-by-step process. I wrote a tutorial on how to perform this method using R, which is available on my RPubs page (link).

Reference:

Altman DG, Bland JM. Interaction revisited: the difference between two estimates. BMJ. 2003 Jan 25;326(7382):219. doi: 10.1136/bmj.326.7382.219. PMID: 12543843; PMCID: PMC1125071.

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Pharmacist labor market using supply and demand curves

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Introduction

Pharmacists are specialized health professionals with a Doctor of Pharmacy (PharmD) degree. Pharmacists are generally viewed as medication dispensing specialist, but they also monitor for potential drug-drug interactions, provide vaccinations, manage therapy for patients with chronic disease, and in some states, provide and deliver healthcare directly to patients. As the role of the pharmacist expands, the demand also has increased.

There has been a lot of research to understand the pharmacist labor market. In the early 2000s, reports indicated that there was a pharmacist shortage, which was fueled by the growing number of the senior citizen population and increased number of prescriptions.[1–3] This concern of a pharmacist labor market shortage, which was unable to meet the demand of a growing Medicare population, led to an increase in the number of Doctor of Pharmacy Schools in the United States from 80 in 2000 to approximately 140 in 2020.[4]

However, pharmacy school enrollment has been dwindling, which threatens the labor market supply. For instance, the number of applications to pharmacy schools dropped by 36% from 2012 to 2021.[5] This has led to some pharmacy school closures in recent years.[6,7] Further, the California Board of Pharmacy reported staffing levels at community pharmacies were dangerously low and could threaten patient care and safety.[8]

Microeconomic theory can provide some insights into the evolving pharmacy labor market. By using simple supply and demand curves, we can illustrate how these factors can impact the wages and quantity of pharmacists in the labor market.

Supply and Demand

The pharmacist labor market can be explained by the demand needed for their services and the number of available pharmacists in the workforce. It can also be explained by the supply of pharmacists currently in the market or entering the market.

Demand can be due to the expanding role of the pharmacist to provide innovative healthcare to their community, the growing senior citizen population, and the rise in prescriptions ordered and dispensed. Demand for pharmacist can also increase due to their evolving roles as practitioners.  

Likewise, the supply of pharmacists in the workforce will depend on several factors such the number of new pharmacists entering the market (e.g., pharmacy school graduates) and the current supply that are already in the workforce. The supply of pharmacists will also be impacted by the number who retire or burnout and pursue other activities such as administrative roles.

We can use simple supply and demand curves to illustrate how the market (e.g., wages and quantity) can be impacted by things like a decrease in the enrollment and graduation of pharmacy students, the shrinking number of pharmacists due to retirement or leaving the workforce due to burnout, evolving role of pharmacists, and the increased number of senior citizens enrolled in Medicare.

Wages are important because this can incentive individuals to pursue a pharmacist career. If the wage is high enough, they are incentivized to enroll into a pharmacy school and become a pharmacist. However, if the wages are too low, then individuals are less likely to pursue a career in pharmacy. Likewise, firms will need to pay higher wages for pharmacists if there is a shortage and high demand for them in the market.

 

Simple example

In this simple illustration, the supply and demand curves are plotted along the wage (W) and quantity (Q) axes (Figure 1).

Figure 1. Simple demand and supply curves.

We can think of there being two players in this pharmacist labor market: Firms (employers) and pharmacists (employees). Pharmacies (e.g., firms/employers) have a need to hire pharmacist to deliver healthcare services, and pharmacists (employees) have a need for pharmacies to hire their labor. The demand and supply curves provide a visual approach to determine the ideal wage and quantity of pharmacists in the market.

The supply curve is upward sloping. As the wage of the pharmacist increases, there is an incentive to increase the quantity of pharmacists in the market. Individuals will go to pharmacy school and complete their training to become pharmacists. Likewise, pharmacy schools may increase enrollment or new pharmacy schools may open to meet the demand.

The demand curve is downward sloping. As the wage of the pharmacist decreases, there is very little to no incentive to become a pharmacist, thus, the quantity of pharmacists decreases. Conversely, if there is a high demand for pharmacists, then the firms will pay a higher wage in order to incentivize individuals to enter the pharmacist workforce.

The point where the supply and demand curves intersect is the equilibrium point. This is where the equilibrium wage (W*) and the equilibrium quantity (Q*) are determined. At the equilibrium wage W*, there should be an equilibrium quantity (Q*) of pharmacists in the labor market.

There are several assumptions we have to make with this simple example. First, this is a perfectly competitive market. This means that there are many firms or employers who will hire pharmacists. Second, market forces determine the wages in the pharmacist labor market. This means that pharmacists (employees) and firms (employers) are wage takes (not wage setters). Lastly, there is perfect information in the sense that both the firm and pharmacist know what the wages and quantity needed are or should be in the market.

With those things in place, we can see how the market can impact the wages and quantity of pharmacists in the workforce.

 

Factors that affect supply

It’s clear that the supply of pharmacists in the market will depend on the number of graduates and the current rate of pharmacist who retire. But there are other factors that can impact the supply of pharmacist in the labor market. For instance, pharmacists may work part-time thereby reducing the number of available pharmacists for the workforce. Pharmacists may also take on other non-patient care roles such as administration. Low enrollment and school closures can also affect the quantity of pharmacist in the market. Further, increased student debt may dis-incentivize individuals to pursue a career as a pharmacist.

When these factors occur, there is a shift in the supply curve to the left (Figure 2). This shift (S -> S') changes the equilibrium wage (W*) and quantity (Q*) of pharmacists to be higher and lower, respectively. As the supply of pharmacists in the labor market decreases, then the market will respond by setting a higher wage (W') but at a lower quantity (Q') of pharmacists. Alternatively, firms are willing to pay a higher wage for pharmacists due to a decrease in the labor supply.

Figure 2. Supply curve shifts to the left due to a shortage.

Conversely, there could a surplus of pharmacists in the workforce, which means that there are so many pharmacists that firms don’t need them. Alternatively, the large quantity of pharmacists shifts the supply curve to the right (S -> S''). This is illustrated in Figure 3. When the supply curve shifts to the right, the wage of the pharmacist becomes lower (W'') at the new quantity of pharmacists (Q'') that are hired by the firm. Having a lot of pharmacists is good for the firms since they can hire more at a lower wage. But this will disincentive individuals from pursuing a career in pharmacy.

Figure 3. Supply curve shifts to the right due to a surplus.

Factors that affect demand

But what about the factors that affect the demand of pharmacists in the workforce? How will that impact the wage and quantity?

Let’s consider a scenario where the senior citizen population is increasing and there is a need for pharmacists to educate them on their medications. Pharmacies are expecting a large number of Medicare Patients to also enroll in their Medication Therapy Management (MTM) plans where the pharmacist will be their main healthcare contact and provider. The expanding role of pharmacists and the increasing number of patients both contribute to the demand of pharmacists. This has an impact of the demand curve and shifts this to the right, D -> D'. Figure 4 illustrates the shift in the demand curve to the right where the wage of the pharmacist has increased to W' and the quantity hired has increased to Q'. In other words, firms are paying higher wages for pharmacist to fill critical roles in their pharmacies, which results in more pharmacists being hired to meet the increase in demand.

Figure 4. Demand curve shifts to the right due to an increase in the demand for pharmacists.

However, the demand or need for pharmacists can decrease due to market forces. The evolution of artificial intelligence and robotics may decrease the demand of pharmacists. Should this scenario occur, the demand for pharmacists will decrease, which is represented by a shift in the demand curve to the left (D -> D''). Figure 5 illustrates the impact that a decrease in the demand curve will have on the wage and quantity of the pharmacist in the workforce. As the demand curve shifts to the left, the wage (W'') is lower and the quantity (Q'') of pharmacists is also lower. This means that firms are going to hire less pharmacists at a lower wage due to a decrease in the demand.

Figure 5. Demand curve shifts to the left due to a decrease in the demand for pharmacists.

Simultaneous shifts in the supply and demand

So far, we only looked at the effects that supply and demand would have on the pharmacy labor market independently of each other. But what is both the supply and demand are affected at the same time? What would happen to the pharmacy labor market in terms of wages and quantity hired?

Let’s consider a scenario where there is a shortage of pharmacists in the labor market, but the demand has increased due to an increasing number of senior citizens enrolled in Medicare (Figure 6). This would cause the supply curve to shift to the left (S -> S''') and the demand curve to shift to the right (D -> D'''). This would result in firms hiring more pharmacists (Q''') at a higher wage (W''').

Figure 6 illustrates what would have if there was a shortage of pharmacists and the demand increased.

We can consider the opposite effect where the demand of pharmacists decreases (or shifts to the left) and the supply increases (or shifts to the right). This would result in a depression in wages and a small increase in the quantity of pharmacists being hired (Figure 7). Firms will hire slightly more pharmacists at depressed wages due to a simultaneous decrease in demand and an increase in the supply of pharmacists in the workforce. I think of this as a worst-case scenario for the pharmacist profession.

Figure 7. Impact of decreased demand and increased supply of pharmacists in the workforce.

But that’s not all!

These shifts in the supply and demand curves are predictions. What if the shifts are greater? 

Let’s consider an example where both the supply and demand curves have shifts that are greater than the examples above. In Figure 8, the supply curve shifts to the left in an extreme manner (e.g., a large number of pharmacists are leaving the workforce), and the demand curve shifts to the right in an extreme manner (e.g., the need for pharmacists has increased dramatically due to an increase in the senior citizen population). The wage (W''') has gone up dramatically and the supply (Q''') is now lower than original equilibrium quantity (Q*). Compare this to Figure 6 where the supply (Q''') was greater than the original equilibrium quantity (Q*).

Figure 8. Impact of both the supply and demand curves are ambiguous depending on the amount of the shifts.

This demonstrates to us that when both the supply and demand curves shift, we really don’t know what’s going to happen. Our predictions will depend on how much these curves shift and in what direction. To understand the effects of both the supply and demand curves of pharmacists shifting, we will need data.

Conclusions

Using simple illustrations of the supply and demand curves, we can visualize how the market would react to changes in the demand and supply of pharmacists in the workforce. We have to assume that the pharmacist labor market is in perfect competition. However, in the real-world, that doesn’t always occur. For example, studies have evaluated the impact of consolidation of (large retail chain) pharmacies that could control the market and force pharmacists to accept the wages they offer (monopsony).[9,10] This can violate the assumption of a pharmacist labor market being in perfect competition and seriously disadvantage pharmacists from not being able to negotiate fair wages. Moreover, when both the supply and demand curves shift, the effects on wages and quantity of pharmacists in the workforce is ambiguous; we will need data to understand what will happen to the pharmacist labor market. Regardless, by using these simple methods, we can start to understand how markets should behave in ideal conditions and when to identify when these markets are failing us, thereby requiring some policy intervention to make things more fair.

 

References

1. Knapp KK, Quist RM, Walton SM, Miller LM. Update on the pharmacist shortage: national and state data through 2003. Am J Health Syst Pharm. 2005;62(5):492-499. doi:10.1093/ajhp/62.5.492

2. Knapp KK, Livesey JC. The Aggregate Demand Index: measuring the balance between pharmacist supply and demand, 1999-2001. J Am Pharm Assoc (Wash). 2002;42(3):391-398. doi:10.1331/108658002763316806

3. Taylor TN, Knapp KK, Barnett MJ, Shah BM, Miller L. Factors affecting the unmet demand for pharmacists: state-level analysis. J Am Pharm Assoc (2003). 2013;53(4):373-381. doi:10.1331/JAPhA.2013.12130

4. Brown DL. Years of Rampant Expansion Have Imposed Darwinian Survival-of-the-Fittest Conditions on US Pharmacy Schools. Am J Pharm Educ. 2020;84(10):ajpe8136. doi:10.5688/ajpe8136

5. Pharmacy College Application Service. 2021-2022 - PharmCAS Applicant Data Report. Accessed December 17, 2023. https://connect.aacp.org/discussion/pharmcas-applicant-data-for-2021-2022

6. Harsa C. Husson University to close its pharmacy school. newscentermaine.com. February 17, 2025. Accessed June 22, 2025. https://www.newscentermaine.com/article/news/education/husson-university-pharmacy-school-program-university-of-new-england-students-maine/97-665e64a5-ecb9-44ea-a1ed-187e6fb495a7

7. American Association of Colleges of Pharmacy. Pharmacy Schools Are Essential to Meeting Growing Demand for Pharmacists’ Services. Accessed June 22, 2025. https://www.aacp.org/article/pharmacy-schools-are-essential-meeting-growing-demand-pharmacists-services

8. California Board of Pharmacy. Pharmacy Workforce Survey, 2021. California Board of Pharmacy; 2021. Accessed December 18, 2023. https://www.pharmacy.ca.gov/meetings/agendas/2021/workforce_presentation.pdf

9. Farag E, Steinbaum M. A Retrospective Analysis of the Acquisition of Target’s Pharmacy Business by CVS Health: Labor Market Perspective. Published online November 25, 2023. doi:10.2139/ssrn.4644895

10. Bounthavong M. Despair and hope: Is the retail community pharmacy workforce in danger of becoming a monopsony labor market? J Am Pharm Assoc (2003). 2024;64(3):102039. doi:10.1016/j.japh.2024.02.012

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Transform data from wide to long format using R

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Often, when we input data into a spreadsheet, we use the wide format where the sequence of variables are ordered according to the columns. But when we perform longitudinal analyses, we need to transform this to the long format.

Sometimes, I forget how to do this in R, so I decided to write a tutorial to remind myself how to do this.

Therefore, I wrote a tutorial on using the pivot_longer() function to transform data from the wide to long format in preparation for longitudinal data analysis. The tutorial is located on my RPubs page.

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Generate data using the simstudy package in R

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There are times when you are looking for a dataset to test a code or formula, but they are hard to find or are not publicly available. To get around this problem, we can generate our own data. R provides several tools for us to accomplish this.

I wrote a short guide on how to generate data using the simstudy package in R. You can read how to do this on my Rpub site (link).

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Medication adherence estimations using R - Part 1

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I created a tutorial on how to use the AdhereR package in R to estimate the medication adherence rate for a sample of individuals with prescription claims data. I posted the tutorial on my RPubs page (link).

The two most common medication adherence meaures are the Medication Possession Ratio (MPR) and the Proportion of Days Covered (PDC). This tutorial reviews how to estimate these medication adherence rates using AdhereR in R.

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Propensity score matching in R

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I wrote an introductory tutorial on how to perform propensity score matching using R, which has been posted on my RPubs site (link).

Propensity score matching is a statistical approach to balancing the observed covariates between groups. In observational studies, this method has the potential to mitigate potential confounding and allow us to make causal interpretations. However, there are a lot of approaches and nuances. This intorductory tutorial presents the basics of propensity score methods and how we can use these in our conventional analyses.

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Stata - marginsplot & mplotoffset commands for plotting average marginal effects

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In Stata, users have a lot of flexibility with creating plots, particularly after the margins command has been executed. Once a regression command has been run, users can estimate the average marginal effect of a factor with respect to another variable using the margins command in Stata. Once the average marginal effect has been estimated, users can plot this using the marginsplot or mplotoffset commands. These are power tools that allow us to visualize the average marginal effects, particularly when we have interaction terms.

I posted a tutorail on my RPubs site that revieweed some basic features of the marginsplot and mplotoffset commands and provide some practical examples of customization.