Takakuwa, Kevin M. MD; Biros, Michelle H. MD, MS; Ruddy, Richard M. MD; FitzGerald, Michael PhD; Shofer, Frances S. PhD
Emergency medicine (EM) is a relatively new specialty. The American Board of Emergency Medicine (ABEM), the credentialing body for EM, was incorporated in 1976 and certified its first physicians in 1980.1 By 2008, 57% of active emergency department (ED) physicians were EM board certified, and an additional 12% were EM trained. The 2007 Institute of Medicine report “Hospital-Based Emergency Care: At the Breaking Point” demonstrated the EM workforce needs,2 and subsequent ED report cards confirmed the shortages of EM specialists.3,4 Together, these publications supported the American College of Emergency Physicians’ claim that “there is currently a significant shortage of physicians appropriately trained and certified in emergency medicine.”5 The Association of American Medical Colleges (AAMC) also reported this shortage in a 2009 report.6 The ABEM estimated that the EM physician shortage will continue for another 30 or more years.1
EM is unique in that it has different workforce needs than the other specialties facing similar workforce shortages. First, EDs require around-the-clock staffing, which can negatively affect the sleep patterns, health, personal and work–life balance, and satisfaction of EM physicians.7 Second, academic EM physicians work in an environment with high patient volumes, high-acuity patients, and often long wait times for patients to see a licensed practitioner.8 Because of these environmental factors, researchers have studied stress and burnout in EM physicians for more than 20 years.9–12 Two such recent studies indicated that one-third of EM physicians show signs of career burnout.13,14 Accompanying these high levels of stress and burnout are increases in ED annual volume nationwide,15 decreasing numbers of EDs and hospitals,16 and the challenges associated with caring for an aging U.S. population.17
Because EM is a relatively new specialty with unique characteristics, we know little about the working life span of EM physicians and the changes occurring as the first generation of EM-trained physicians age.18 In 2008, the average age of practicing EM physicians was 49 years old.4 In addition, the negative consequences of rotating shifts common in EM appear to be more pronounced as physicians age.19 Whereas researchers have documented the impact of aging on physicians’ medical practice, they have not specifically addressed shift work disorders (circadian rhythm sleep disorders and other sleep deprivation health-related issues), which are more prevalent in EM physicians.19
As part of its efforts to address issues related to the academic EM workforce, the Society for Academic Emergency Medicine (SAEM) created an Aging and Generational Issues taskforce for the 2009–2010 academic year. One of the missions of this taskforce was to describe current issues related to a multigenerational workforce with aging faculty and, hopefully, to determine potential solutions to these issues.
An important component of this process was to survey formally academic EM leaders to determine how these issues currently are being addressed and what knowledge gaps exist to drive future research. The primary aim of this study was to describe the existing policies, practices, and attitudes of academic EM leaders on workforce issues, shift work, and accommodating the academic and personal needs of aging physicians practicing in a multigenerational work environment. Our secondary aim was to understand how EM leaders dealt with other faculty circumstances that could affect personal and professional scheduling, such as life events, illness, and a desire to work part-time.
In 2009, we conducted a national survey of the leaders at EM residency programs accredited by the Accreditation Council for Graduate Medical Education (ACGME).20 We invited the department chair or the division chief or division head, for those without department status, at each program to complete our survey. In this report, we refer to all survey participants, regardless of title, as “EM leader.”
Survey content and administration
The Aging and Generational Issues taskforce developed a prospective survey in July 2009, with our input on survey design and implementation. The survey gathered demographic information on the respondents, asked respondents to define the ages of the EM physicians in their programs and to describe how they staff their off-hour clinical shifts, and assessed their programs’ policies and practices and their attitudes related to aging EM physicians.
The survey went through expert review in August and September 2009, which included distribution first to the Aging and Generational Issues taskforce members, then to several members of the SAEM board of directors. The reviewers examined the survey to identify any potential problems in the wording and structure of the questions and to determine whether the items included in the survey adequately addressed the research objectives. At least 10 people provided feedback, which led to at least two survey instrument modifications. The survey had 38 total questions divided into six main sections: (1) respondent demographic information, (2) description of ED staff by age and employment status, (3) faculty preferences for overnight or weekend shifts, (4) accommodations made for aging faculty, (5) factors used to determine such accommodations (age, academic rank, and academic position/role), and (6) respondent’s attitudes toward different clinical shifts. Most responses included discrete options (menu choices, yes/no), but a few allowed for open-ended answers (see Supplemental Digital Appendix 1, http://links.lww.com/ACADMED/A113). The survey instructions directed respondents to report both formal and informal policies at their institutions. The SAEM board of directors and the institutional review board at Jefferson Medical College of Thomas Jefferson University approved this survey and our study.
Data collection and processing
To conduct our study, we used an online survey instrument (SurveyMonkey, Portland, Oregon). We collected e-mail addresses for our EM leaders by compiling a list of approved EM residency programs from the ACGME, comparing that list with one already generated by SAEM, and verifying current EM leaders via program Web sites. We obtained e-mail addresses that we could not verify through program Web sites by telephoning the EM programs directly.
In September 2009, shortly before the final survey was sent out, all EM leaders received an e-mail notice introducing the upcoming survey authored by the Aging and Generational Issues taskforce. This advance e-mail asked leaders to gather the ages of their faculty members and to be prepared to answer questions related to their faculty members’ work practices. In mid-October 2009, we distributed the survey to all 146 identified EM leaders.
Although responses were anonymous, we used unique identifiers to track completions. We sent follow-up e-mails to nonresponders after two weeks and in January and March 2010. In early 2010, we telephoned all EM leaders or their assistants at least twice, again to encourage nonresponders to complete the survey. To increase the response rate further, the Aging and Generational Issues taskforce offered to conduct the survey by telephone or to mail a hard copy if the EM leader preferred either method of response. The taskforce members also sent individualized e-mails to those leaders whom they knew personally, to encourage participation.
We calculated univariate descriptive statistics, including frequency and percentage distributions, for each closed-ended question, along with standard deviations for continuous data. We identified common themes from the open-ended responses using a thematic coding process. We analyzed bivariate comparisons by age, gender, or years as an EM leader with chi-square or Fisher exact test for categorical data. We performed all analyses using SAS statistical software (version 9.1, SAS Institute, Cary, North Carolina). We considered P < .05 to be statistically significant.
A total of 89 of 146 invited EM leaders responded. Two refused to participate, and 9 submitted incomplete surveys, resulting in 78 completed surveys and a 53% response rate. The mean age of respondents was 54.4 ± 7.2 years old. We stratified respondents into two categories: “younger” (<55 years old) and “older” (≥55 years old). Respondents included 9 women (12%). Seventy-six respondents (97%) were white, 1 (1%) did not identify a race, and 1 (1%) did not identify a race but we subsequently identified him or her as Asian based on our personal knowledge of the respondent. Respondents served as department leaders for a mean of 10.2 ± 7.9 years. We stratified respondents into two categories: “junior EM leaders” (<10 years of experience) and “experienced EM leaders” (≥10 years of experience).
Description of workforce
Respondents reported that the average minimum number of clinical hours worked per year to be considered a full-time employee at their respective institutions was 1,120 ± 392 hours (range 400–1,834 hours). Table 1 includes the age distribution of clinical faculty for all 78 institutions. EM leaders’ qualitative responses included reasons cited by part-time staff for choosing to work fewer hours, including family commitments/children, other full-time jobs, lifestyle/personal choice/preference, staying connected to an academic environment, dual appointments in other departments, other career/going to school, limited availability of clinical shifts, older age, low pay, disability/health problems, and staffing the ED during department staff meetings.
Staffing of off-hour clinical shifts
Seventy-three percent (56/77) of EM leaders reported employing physicians who work primarily overnight shifts. These physicians represented a mean of 3.4 full-time positions per site and had a mean age of 40.4 ± 5.2 years. They also were better compensated at 71% (39/55) of institutions, including a salary differential (a fixed dollar amount and/or percentage increase), credit or reduction in total number of shifts worked, and the ability to set their own schedules. Respondents cited the following reasons for their faculty choosing to work primarily overnight shifts, including better pay, fewer clinical work requirements, personal preference, more time with family, perceived ease of working without daytime administration present, more independence, ability to set schedule, the only available shifts for part-time physicians, and more freedom during daytime hours for administration, research, or a second job. One EM leader added:
I think trying to minimize nights in the older faculty member is important, but it cannot be done on the backs of developing junior faculty—that is not an approach for departmental success. For us, having a couple of people who do mainly nights—by preference—has gotten overall night shifts down to two maximum per month, and even our older faculty seem to be able to tolerate that with proper scheduling and measures to combat the disruptive nature of night shifts (e.g., make sure nothing is scheduled the day after a night shift).
Thirty percent (23/77) of EM leaders have some physicians who work primarily weekend shifts. These physicians represented 2.0 full-time positions per site and had a mean age of 46.8 ± 9.6 years old. They also were better compensated at 17% (4/23) of institutions, by the same methods used to compensate those who work overnight shifts. Respondents cited similar reasons for their faculty working weekend shifts as working overnight shifts, including fewer clinical work requirements, personal preference, more time with family, another job during the weekdays, ability to set schedule, use of weekend shifts instead of overnight shifts, and weekend shifts that leave more weekday time free for administration, research, or a second job.
Policies for aging faculty
Twenty-five percent (19/77) of EM leaders reported having a formal department policy to accommodate aging faculty, whereas 36% (28/77) reported having an informal department policy. Three programs had both formal and informal policies. See List 1 for a brief description of both these formal and informal policies.
Eight percent (6/77) of EM leaders reported assigning special roles or duties to aging faculty. These roles included working fast-track shifts and shifts in lower-acuity areas of the ED, providing faculty development and mentorship, added administrative duties to replace clinical shifts, and educating students.
Eighteen percent (14/77) of EM leaders reported having university or hospital policies that limited their ability to provide flexibility for their full-time staff. These policies included a cost-of-benefits-mandated minimum level of work, an institutional oversight committee on staffing, faculty governed by union membership, and limited staff to cover all shifts.
When we stratified policies for aging faculty by the EM leader’s age, gender, and years as an EM leader, a greater number of junior EM leaders reported having university or hospital policies that limited their ability to provide flexibility for their full-time faculty (26% [10 of 39] versus 11% [4 of 38] of experienced EM leaders, P = .08). They also reported having a greater number of informal department or division policies to accommodate aging faculty (49% [19 of 39] versus 26% [10 of 38] of experienced EM leaders, P = .06).
Practices for accommodating faculty
Fifty-eight percent (45/77) of EM leaders had accommodated an aging physician who was not able to work certain types of shifts. The most common methods they used included decreasing or eliminating overnight shifts and allowing the physician to decrease his or her overall number of clinical hours or become a part-time employee (see List 2 for other methods).
Seventy-one percent (55/77) of EM leaders had accommodated a physician for reasons not related to age. Respondents cited two reasons for doing so: either family issues (pregnancy, new paternity, single parents, divorce, child care issues, or family emergencies), or disability or medical issues (surgery, heart attack, depression, cancer, Parkinson disease, psychiatric disorders, diabetes and hypertension worsened by overnight shifts, paraplegia, sleep disorders, or physical injuries). Methods of accommodation for non-age-related issues were similar to those for age-related ones. Respondents also cited hiring temporary physicians to fill in for the physician, a payback system for missed shifts, and a policy of dividing missed shifts among other faculty members.
Thirteen percent (8/64) of EM leaders stated that making accommodations for some physicians because of age or any other reason led to issues with other faculty. Such issues included young/healthy faculty expressing negative feelings when asked to work extra shifts, a feeling of unfairness, and the perception that accommodations were too generous or that the individual was not doing everything he or she could to return to full-time status. EM leaders (34/78; 44%) also shared recommendations for helping aging physicians achieve a more manageable schedule (see List 3). When we stratified practices for accommodating faculty by the respondent’s age, gender, and years as an EM leader, experienced EM leaders had a greater number of recommendations (21 of 38 [55%] versus 12 of 38 [32%] junior EM leaders, P < .05).
Attitudes on staffing clinical shifts
Table 2 summarizes respondents’ attitudes toward staffing clinical shifts related to age, academic rank, and department academic position/role. Respondents cited specific faculty characteristics to consider when reducing shifts for faculty, including grant support, extra- or intramural funding, institutional roles, or any activity that brings revenue to the ED; research time, grant applications, and research productivity, including publications; teaching and educational responsibilities; administrative responsibilities within the ED (emergency medical services director, quality assessment and improvement director, program director, medical student education director, clinical director) and hospital (committee work, leadership roles); and national leadership roles.
EM leaders described a number of factors that affected the types of shifts worked by faculty, including the need for certain faculty with teaching, administrative, and research responsibilities to be available during the daytime; accommodating those with evening, overnight, and weekend preferences; considering age and interest in deciding who covers lower-acuity areas and the fast track; allowing the department chair to forgo working overnight and weekend shifts and to pick his or her shifts; making accommodations but using pay differentials; and providing some protected time for junior faculty to develop grants. In addition, several responses directly addressed the concerns of some faculty that it is unfair if the overnight and weekend shifts are not shared equally by all faculty, regardless of other commitments, because of the burden it places on the remaining faculty members. One EM leader stated it more bluntly:
If the chair doesn’t do his or her fair share of the problem shifts, I feel it will be harder on the faculty to deal with shift work. You should have asked if what is good for the goose is good for the gander. I do nights and weekends, many other department chairs don’t, and I’ll bet the responses vary with those different frames of reference.
A greater number of junior EM leaders disagreed that age should be considered when assigning shift types (24% [9/38] of junior EM leaders were against using age versus 8% [3/37] of experienced EM leaders). Similarly, 5% (2/38) of junior EM leaders were neutral about using age in such designs compared with 19% (7/37) of experienced EM leaders. One EM leader stated:
This is a leadership issue; push-back from junior staff is expected. Reminding junior staff that their work is evaluated independently of others’ work is necessary. Complaints about fairness should be met with some general discussion of the overall value to the enterprise from the different work of each doctor and a reminder of Jimmy Carter’s quote: “Life isn’t fair.” Leaders must lead and that includes managing expectations. Leadership is challenging and often uncomfortable.
We conducted this survey to determine both how academic EM leaders understand the context of running a 24-hour, seven-day-a-week ED and the ways in which the academic ED has evolved to accommodate the staff and their needs to sustain longevity and productivity in today’s health care environment. One EM leader described the situation well: “This will be a big challenge for the specialty in the coming decades. We will need to think of new models since the demands of the clinical practice really take their toll over time.” As such, the SAEM Aging and Generational Issues taskforce sought to better understand the relationship between aging EM physicians and the large talent pool of younger physicians, who may have different values and life requirements, as departments consider how to develop future leaders. These issues related to the differences between generations and running an academic ED today, including the recruitment and retention of EM physicians across the entire professional age range, have recently been described in a set of articles by the SAEM Aging and Generational Issues taskforce.21,22 To supplement those articles, we believe that the findings of our study provide information that is relevant to other specialties that have transitioned from an on-call model to shift work, such as hospital medicine, critical care, neonatology, and surgical specialties. In addition to these fields, trainees also experience shift work now with the ACGME’s changes in duty hours requirements.23,24
The results of our survey suggest that planning for and distributing the clinical workload across the workforce is critical to recruiting and retaining faculty. For example, modifying an older faculty member’s off-hours clinical workload to accommodate his or her age or other factors indicates to younger physicians that the department will meet their evolving personal and professional needs in the future. The EM leaders in our study recognized that the success of their departments depends on a healthy and satisfied faculty. To achieve this goal, they must creatively manage work-related issues, such as avoiding both the use of different tracks for each “special issue” as it arises and the “one-size-fits-all” approach of past decades.
The results of our survey also indicate that virtually all respondents work with generous faculty who support their fellow faculty when short-term illness and other personal crises arise, and that they do so even when no formal policy exists to cover these unforeseen events. In addition, EM leaders reported trying to specifically recruit and retain “night owls,” compensating them in different ways for their nights-only work. Previous research has suggested that those who are intolerant of shift work tend to select themselves out (i.e., by eventually leaving their jobs)25; yet, EM physician “night owls” likely are better able to tolerate shift work, and therefore they may self-select into this role. This observation, and the duration of overnight shift tolerance throughout an EM physician’s career, has not been studied, although researchers have shown that residents’ cognitive function decreases after repeated overnight shifts.26 Yet, most respondents did recognize that overnight shifts may interfere with the academic productivity of the individuals within their department regardless of their academic rank.
Next, respondents acknowledged that aging makes shift work harder. That age is a risk factor for shift work disorder has been acknowledged in the literature as well.16 Aging reduces our ability to adjust to changes in circadian rhythm and to achieve restorative sleep, which may contribute to increasing fatigue despite working the same number of hours overall.27 In addition, older EM physicians may feel both more pressure and less able to achieve the same high-performing level of practice as the traditional methods of mentorship, teaching, and technology change to meet the needs of younger EM trainees.21 If aging indeed has an impact on the effectiveness and practice performance of EM physicians, we must consider developing productive clinical or nonclinical roles for aging physicians in the often fast-paced, high-stress environment of the ED. Retaining experienced EM physicians and benefiting from their skills and knowledge while also meeting the public’s expectation that EDs deliver the same high-quality health care at all times of day will pose an important challenge for us in the coming years. To achieve this goal in the years to come, we must take advantage of our many assets to maximize the continued development of our academic specialty in an evolving environment.
Finally, we in EM must continue to describe and implement a robust research agenda that will address the issues that are critical to sustaining our field. This work includes the development of paths for master clinicians and researchers within the shift work framework that have the best success and satisfaction profile for faculty. We also should seek out empirical evidence for the ideal shift length and scheduling system by age and other factors, instead of continuing to use the current method of faculty requesting time off for personal or professional responsibilities. In addition, through the science of our teamwork and the culture and leadership across our EDs, we must identify and capitalize on the characteristics that enhance the success of our programs in clinical care, research, and educating the next generation of EM leaders.
First, our survey was completed by only 50% of the targeted EM leaders despite numerous efforts to engage nonrespondents. Although the literature supports that our response rate is in a reasonable range,28,29 we cannot unequivocally state that the responses we received are representative of the leadership in EM. In addition, our respondents represented a fairly homogenous group (i.e., white men over 55 years old). Although this may have been response bias, it more likely reflects the current population of EM leaders, as it is similar to the percentage of women and minority department chairs across institutions as reported by the AAMC in 2008.30 Next, we acknowledge that our survey, which was not previously validated, had to request large amounts of data, was subject to the biases of the respondents completing it, and may not have gathered all the necessary information if a respondent was uncomfortable answering a question. However, our search for a validated survey instrument to use in our study was unsuccessful. In addition, we recognize that we surveyed only the EM leadership and not the staff they represent, whose perceptions may be quite different. Finally, we acknowledge that we did not compare our data with those from private nonacademic EDs, whose faculty members’ perceptions may not be the same as those in our study.
Recruiting and retaining a stable, healthy, and satisfied EM workforce requires that leaders continue to acknowledge staffing issues related to aging, shift work, and physician well-being and work to develop solutions to address these issues. As clinical coverage models change to align more with shift work systems, these issues are becoming increasingly relevant to other specialties as well as EM. Although EM leaders have considered the implications for these issues, they have not developed standardized and validated methods to deal with them. To aging physicians who are working later in life, potentially not having full institutional benefits is both challenging and stressful (i.e., fewer benefits for part-time faculty, having to negotiate for less desirable shifts, having to account for non-revenue-generating tasks). Working overnight shifts is particularly difficult for aging physicians. Determining the value, needs, and longevity of those who elect to work only nights may provide insight into one method of accommodating aging EM physicians. We believe that being open to diversity, maintaining parity without perfect equity, and instituting a form of “promotion” to a schedule better fitting aging physicians’ physical and other needs may benefit academic institutions. The combination of the aging physician, who possesses a great deal of experience, and the junior physician, with a fresh point of view and a high command of newer clinical and procedural skills sets, makes for a great clinical team and one we should work toward in the future.
Acknowledgments: The authors thank the members of the Aging and Generational Issues task force, the SAEM leadership, and the EM leaders who contributed their time and effort to our study.
Other disclosures: None.
Ethical approval: The institutional review board at Jefferson Medical College of Thomas Jefferson University approved our survey and study.
Previous presentations: We presented part of this study at the 2010 SAEM Annual Meeting in Phoenix, Arizona.
2. Institute of Medicine. Committee on the Future of Emergency Care in the United States Health System.Hospital-Based Emergency Care: At the Breaking Point. 2007 Washington, DC National Academies Press
3. Epstein SK, Burstein JL, Case RB, et al. The national report card on the state of emergency medicine: Evaluating the emergency care environment state by state 2009 edition. Ann Emerg Med. 2009;53:4–148
4. Ginde AA, Sullivan AF, Camargo CA Jr. National study of the emergency physician workforce, 2008. Ann Emerg Med. 2009;54:349–359
5. American College of Emergency Physicians.. Emergency medicine workforce. Ann Emerg Med. 2006;48:510
7. Kuhn G. Circadian rhythm, shift work, and emergency medicine. Ann Emerg Med. 2001;37:88–98
8. Kristal SL, Randall-Kristal KA, Thompson BM. 2001–2002 SAEM emergency medicine faculty salary and benefits survey. Acad Emerg Med. 2002;9:1435–1444
9. Gallery ME, Whitley TW, Klonis LK, Anzinger RK, Revicki DA. A study of occupational stress and depression among emergency physicians. Ann Emerg Med. 1992;21:58–64
10. Keller KL, Koenig WJ. Management of stress and prevention of burnout in emergency physicians. Ann Emerg Med. 1989;18:42–47
11. Doan-Wiggins L, Zun L, Cooper MA, Meyers DL, Chen EH. Practice satisfaction, occupational stress, and attrition of emergency physicians. Wellness Task Force, Illinois College of Emergency Physicians. Acad Emerg Med. 1995;2:556–563
12. Goldberg R, Boss RW, Chan L, et al. Burnout and its correlates in emergency physicians: Four years’ experience with a wellness booth. Acad Emerg Med. 1996;3:1156–1164
13. Kuhn G, Goldberg R, Compton S. Tolerance for uncertainty, burnout, and satisfaction with the career of emergency medicine. Ann Emerg Med. 2009;54:106–113.e6
14. Cydulka RK, Korte R. Career satisfaction in emergency medicine: The ABEM longitudinal study of emergency physicians. Ann Emerg Med. 2008;51:714–722.e1
15. Pitts SR, Niska RW, Xu J, Burt CW. National hospital ambulatory medical care survey: 2006 emergency department summary. Natl Health Stat Report. August 6, 2008:1–38
16. Kellermann AL. Crisis in the emergency department. N Engl J Med. 2006;355:1300–1303
17. Schumacher JG. Emergency medicine and older adults: Continuing challenges and opportunities. Am J Emerg Med. 2005;23:556–560
18. Reinhart MA, Munger BS, Rund DA. American Board of Emergency Medicine longitudinal study of emergency physicians. Ann Emerg Med. 1999;33:22–32
19. Sack RL, Auckley D, Auger RR, et al.American Academy of Sleep Medicine. Circadian rhythm sleep disorders: Part I, basic principles, shift work and jet lag disorders. An American Academy of Sleep Medicine review. Sleep. 2007;30:1460–1483
20. Accreditation Council of Graduate Medical Education. . List of ACGME accredited programs and sponsoring institutions. http://www.acgme.org/adspublic/
. Accessed October 12, 2012
21. Mohr NM, Moreno-Walton L, Mills AM, Brunett PH, Promes SBSociety for Academic Emergency Medicine Aging and Generational Issues in Academic Emergency Medicine Task Force. . Generational influences in academic emergency medicine: Teaching and learning, mentoring, and technology (part I). Acad Emerg Med. 2011;18:190–199
22. Mohr NM, Smith-Coggins R, Larrabee H, Dyne PL, Promes SBSociety for Academic Emergency Medicine Aging and Generational Issues in Academic Emergency Medicine Task Force. . Generational influences in academic emergency medicine: Structure, function, and culture (part II). Acad Emerg Med. 2011;18:200–207
23. Wagner MJ, Wolf S, Promes S, et al. Duty hours in emergency medicine: Balancing patient safety, resident wellness, and the resident training experience: A consensus response to the 2008 Institute of Medicine resident duty hours recommendations. Acad Emerg Med. 2010;17:1004–1011
24. Philibert I, Friedmann P, Williams WTACGME Work Group on Resident Duty Hours. Accreditation Council for Graduate Medical Education. . New requirements for resident duty hours. JAMA. 2002;288:1112–1114
25. Marquié JC, Foret J. Sleep, age, and shiftwork experience. J Sleep Res. 1999;8:297–304
26. Machi MS, Staum M, Callaway CW, et al. The relationship between shift work, sleep, and cognition in career emergency physicians. Acad Emerg Med. 2012;19:85–91
27. Costa G, Di Milia L. Aging and shift work: A complex problem to face. Chronobiol Int. 2008;25:165–181
28. Johnson T, Owens L. Survey response rate reporting in the professional literature. Paper presented at: 58th Annual Meeting of the American Association for Public Opinion Research. May 2003 Nashville, Tenn http://www.srl.uic.edu/publist/Conference/rr_reporting.pdf
. Accessed October 12, 2012.
29. Baruch Y. Response rate in academic studies—A comparative analysis. Hum Relat. 1999;52:421–438