A list of a number of our articles follows, along with brief summaries. Clicking on an article's title will open up a .pdf file containing the entire article.
Becker, B.E., & Huselid, M.A. 2006. Strategic Human Resources Management: Where Do We Go From Here? Journal of Management, Vol. 32 No. 6.
In this article, Becker and Huselid identify the key challenges facing Strategic Human Resources Management and discuss several new directions in both scholarship and practice. They argue for a clearer articulation of the "black box" between HR and firm performance and the importance of integrating strategy implementation in this process. They also highlight the importance of a differentiated HR architecture within firms as well as across them.
According to the authors, the practice of HR strategy has moved beyond whether or not there is a significant return to better workforce management – with managers now asking questions like, "What are the key strategic positions in our organization, and how should they be managed?" and "How can we design and implement a workforce management system that helps us execute strategy and create wealth?" They further argue that, although SHRM was initially an HR-centric paradigm, it is rapidly moving out of the hands of HR professionals and into the hands of line managers and senior executives.
Huselid, M.A., Beatty, R.W., & Becker, B.E. "A Players" or "A Positions"? The Strategic Logic of Workforce Management (HBR OnPoint Enhanced Edition). Harvard Business Review, December, 2005.
Companies simply can't afford to have "A players" in all positions. Rather, businesses need to adopt a portfolio approach to workforce management, systematically identifying their strategically important (or "A") positions, supporting (or "B") positions and surplus (or "C") positions, then focusing disproportionate resources on making sure "A players" hold "A positions". This is not as obvious as it may seem, because the three types of positions do not reflect corporate hierarchy, pay scales, or the level of difficulty in filling them. "A positions" are those that directly further company strategy and, less obviously, exhibit wide variation in the quality of the work done by the people who occupy them.
Why variability? Because raising the average performance of individuals in these critical roles will pay huge dividends in corporate value. If a company like Nordstrom, for example, whose strategy depends on personalized service, were to improve the performance of its frontline sales associates, it could reap huge revenue benefits. "B positions" are those that support "A positions" or maintain company value. Inattention to them could represent a significant downside risk. (Think how damaging it would be to an airline, for example, if the quality of its pilots were to drop.) Yet investing in them to the same degree as "A positions" is ill-advised because "B positions" don't offer an upside potential. (Pilots are already highly trained, so channeling resources into improving their performance would probably not create much competitive advantage.) And "C positions"? Companies should consider outsourcing them – or eliminating them. We all know that effective business strategy requires differentiating a firm's products and services in ways that create value for customers. Accomplishing this requires a differentiated workforce strategy, as well.
Huselid, M.A. & Becker, B.E. 2005. Improving HR's Analytical Literacy: Lessons from Moneyball. In The Future of HR: 50 Thought Leaders Call for Change, 278-284. Dave Ulrich, Mike Losey, and Sue Meisinger (Eds). New York: John Wiley and Sons.
In this article, Becker and Huselid use the example of the Oakland Athletics baseball team, as described in Michael Lewis' recent bestseller Moneyball, to illustrate their argument about the need for HR managers to become good strategy managers. They describe how senior Oakland Athletics' executives brought a new "analytical literacy" to their strategic decision-making and redefined what matters and how to measure it, giving their organization a sustained performance advantage over its competitors. Becker and Huselid argue that this lesson has a direct application to senior executives (both HR professionals and line managers) attempting to build the workforce and the HR function into a source of competitive advantage.
Becker, B.E., & Huselid, M.A. Working paper. Value Creation Through Strategy Execution: The Role of SHRM Theory and Practice.
This paper argues that prior theoretical work on the topic of strategic human resource management (SHRM) has not fully elaborated the link between a firm's HR architecture – or overall system of human capital management – and its subsequent financial performance. Drawing on the strategy literature, Becker and Huselid propose explicitly including effective strategy implementation as the key mediating variable in this relationship. This also requires a new focus on the idiosyncratic dimension of HR's strategic fit. These extensions of SHRM theory more completely articulate the HR's impact on value creation by increasing the inimitability of the HR architecture's influence on firm performance.
Becker, B.E., & Huselid, M.A. 2003. Measuring HR? Benchmarking is Not the Answer! Human Resource Magazine, December, 57-61. Lead Article.
HR professionals have routinely relied on benchmarked comparisons of cost and other efficiency-based performance outcomes associated with activities of the HR function to justify their contribution to the organization. In this article, Huselid and Becker argue that a reliance on these types of benchmarking measures not only fails to measure HR's important contributions to firm success, it also encourages an approach to human capital management that is counterproductive.
Instead, Huselid and Becker make the case that HR professionals should judge their performance relative to their firm's own strategy rather than the HR efficiency of other organizations. While common functional benchmarks are safe and easy, they argue that adopting customized strategic performance measures is where HR can truly demonstrate its value.
Richard W. Beatty, Jeffrey R. Ewing, and Charles G. Tharp, Fall 2003. HR'S Role in Corporate Governance: Present and Prospective. Human Resource Management, Vol. 42, No. 3, pp. 257–269.
Corporate wrongdoing is damaging investor confidence and tarnishing the credibility of the U.S. business community, guilty and innocent alike. Some misdeeds are clearly criminal, others simply unethical or damaging to reputations. They range from "massaging" numbers ("managed earnings"), which tests the limits of financial prudence, to outright fraud. Caught in the limelight are U.S. corporate giants representing some of the world's best-known brands and most famous CEOs, many only yesterday lionized in the business press.
This article explores this issue from the perspective of the HR function through a survey of the senior HR professionals who attended the Human Resources Forum. The survey was augmented with focus groups. The purpose was to understand current practices, attitudes, and behaviors with respect to legal standards and professional and ethical codes. We also explored the roles of the CEO, HR leadership, and the HR function in minimizing ethical breaches that have diminished investor and public trust. Beatty, Ewing, and Tharp attempt to shed light on the responsibilities, actions, and risks of the HR function and its leadership now and in the future.
Beatty, R.W., Huselid, M.A., & Schneier, C.E. 2003. The New HR Metrics: Scoring on the Business Scorecard. Organizational Dynamics, 32, 107-121.
This article addresses what and how HR can contribute to the strategic success of firms by transforming itself from a partner (that can be removed or outsourced) to a player on the field, in the game, with the ability to score. The ability to score necessitates a new understanding of the rules of the game – a new perspective on what HR is to contribute, how its systems enable it to contribute, and how its ultimate deliverables can be measured. The rules of the game mean that HR should only attempt to score on an HR Scorecard integrated with the firm's Business Scorecard.
Huselid, M.A., & Barnes, J.E. 2003. Human Capital Measurement Systems as A Source of Competitive Advantage.
An increasing reliance on intangible assets – such as human capital – as a source of competitive advantage has led many firms to develop measurement systems to help them better manage these resources. However, the antecedents and consequences of human capital measurement systems (HCMS) such as Becker, Huselid, and Ulrich's (2001) HR Scorecard methodology are not well understood. Drawing from prior work on the Resource Based View of the firm and the Economics of Information, this article describes the primary attributes of HCMS and develops a conceptual model and series of propositions intended to stimulate research on these systems.
Becker, B.E., Huselid, M.A., & Ulrich, D. 2002. Six Key Principles for Measuring Human Capital Performance in Your Organization. Working paper.
Properly valuing human capital starts with understanding how to measure human capital's contribution to the success of the organization. Based on more than a decade of research, we've demonstrated that when organizations enable, develop and motivate human capital, the result is improved accounting profits and shareholder value. While this research provides a compelling business case for managing human capital like a strategic asset, we find that both HR professionals and line managers often have difficulty translating this academic research into practice.
Managing human capital performance effectively requires new perspectives and new competencies on the part of both line managers and HR professionals. Drawing on their research and work with senior HR professionals and line managers, Huselid, Becker, and Ulrich develop six key principles for measuring human capital performance so that it can be managed as a strategic asset.
Dave Ulrich and Dick Beatty, Winter 2001. From Partners to Players: Extending the HR Playing Field. Human Resource Management, Vol. 40, No. 4, pp. 293–307.
HR professionals must always be "becoming" or constantly changing and adapting. For the last decade, many have argued the business partner role as a complement to traditional HR administrative work. Beatty and Ulrich argue in this paper that HR professionals should move beyond partners to become players. HR professionals as players are "in the game, on the field, making a difference" through their HR work. In this article, the authors suggest that to become players, HR professionals must learn to coach, architect, build, facilitate, lead, and provide a conscience to business leaders. They also describe specific knowledge and tools for each of these roles.
Becker, B.E., Huselid, M.A., & Ulrich, D. 2001. Making HR a Strategic Asset. Financial Times, November, 2001.
Organizations increasingly rely on intangibles as the source of their competitive advantage. R&D, brands, customer relationships, not to mention more abstract "capabilities" like organizational flexibility, are recognized as sources of value creation. Yet, managing these intangibles as assets, in an environment where conventional accounting standards often measures them as costs, is particularly challenging. The solution outlined in this article is to manage HR (Human Resources) as a strategic asset and measure HR performance in terms of its strategic impact. This requires a new perspective on what is meant by HR in the organization and a new understanding of how HR creates value in the organization. Huselid, Becker, and Ulrich argue that both line managers and HR professionals need to think of HR, not in terms of a function, or set of practices, but rather as an "architecture" that must be properly structured and managed in order to create value.
Becker, B.E. & Huselid, M.A. 1999. Overview: Strategic human resource management in five leading firms. Human Resource Management Journal, 38, (4), Winter, 287-301.
This article synthesizes findings from five case studies conducted in firms known to be leaders in the management of people. It draws three broad conclusions: 1. The foundation of a value-added HR function is a business strategy that relies on people as a source of competitive advantage and a management culture that embraces that belief, 2. A value-added HR function will be characterized by operational excellence, a focus on client service for individual employees and managers, and delivery of these services at the lowest possible cost; and 3. A value-added HR function requires HR managers that understand the human capital implications of business problems and can access or modify the HR system to solve those problems.
Artis, C.R., Becker, B.E. & Huselid, M.A. 1999. Strategic human resource management at Lucent. Human Resource Management Journal, 38, (4), Winter, 309-313.
This article describes the HR Management system in place at Lucent Technologies, Inc. Lucent's HR structure is organized around a client service model that focuses on the leaders in the major business units and the movement of as much of the HR infrastructure as possible to these business units. Key emphases include (1) HR operational excellence, (2) compensation and performance management that encourages employees to build a successful future with the firm, as well as to share in that success, and (3) building an operating style and culture that supports Lucent's mission and strategy. Key challenges for the future include (1) organizational renewal in a period of growth, (2) identifying and developing new HR competencies, (3) developing a unique HR structure to support the needs of HR at Bell Labs, and (4) effective labor relations in a rapidly changing industry
Barber, D., Huselid, M.A. & Becker, B.E. 1999. Strategic human resource management at Quantum. Human Resource Management Journal, 38, (4), Winter, 321-328.
This article describes the HR Management system in place at Quantum. Key emphases of Quantum's HR management infrastructure include: (1) establishment and communication of the firm's mission, vision, and values; (2) team-based product development and operations teams; (3) behaviorally based structured interview processes; (4) rigorous and comprehensive performance management and incentive compensation processes; (5) highly automated and efficient HR infrastructure "fundamentals"; and (6) well developed soft asset due diligence processes for integrating mergers and acquisitions. Key challenges for the future include (1) managing explosive growth in a global environment, (2) employee development, (3) managing joint ventures and acquisitions, (4) hiring and retaining talent, and (5) expanding competence in change management processes.
Harris, Barbara, & Huselid, M.A., Becker, B.E. 1999. Strategic human resource management at Praxair. Human Resource Management Journal, 38, (4), Winter, 315-320.
This article describes the human resource management system in place at Praxair. Key emphases of Praxair's HRM infrastructure include (1) competency development and performance-management processes and (2) team-based performance systems, which include four levels of measurement: company-wide, business-unit, cross-functional teams within business units, and special-initiative project teams. Key challenges for the future include (1) prioritization of choices in support of the firm's global growth initiatives, (2) employee development and new talent acquisition, (3) designing more effective methods to anticipate business needs and provide strong, proactive leadership, (4) accelerating leadership development and influencing adequate investment in education and development programs, and (5) designing and implementing effective methods to acquire new talent to support business strategies.
Kirn, S.P., Rucci, A.J., Huselid, M.A. & Becker, B.E. 1999. Strategic human resource management at Sears. Human Resource Management Journal, 38, (4), Winter, 329-335.
This article describes the HR Management System in place at Sears. Key emphases of Sears' HR management infrastructure include: (1) formulating and communicating a corporate mission, vision, and goals, (2) employee education and development through the Sears University, (3) performance management and incentive compensation systems linked closely to the firm's strategy, (4) validated employee selection systems, and (5) delivering the "HR Basics" very competently. Key challenges for the future include: (1) maintaining momentum in the performance improvement process, (2) identifying barriers to success, and (3) clearly articulating HR's role in the change management process.
McCowan, R.A., Bowen, U., Huselid, M.A. & Becker, B.E. 1999. Strategic human resource management at Herman Miller. Human Resource Management Journal, 38, (4), Winter, 303-308.
This article describes the Human Resource Management system in place at Herman Miller, Inc. (HMI). HMI's HR strategy is comprised of three primary goals: (1) building employee capabilities, (2) building employee commitment, and (3) improving the professional capabilities of the HR function itself. Key emphases of HMI's HR management infrastructure include: (1) employee competency identification and development, (2) building employee participation, (3) building business literacy, (4) creating a "corporate community" through strong values and a sense of "belonging", (5) community responsibility and environmental protection, (6) competently delivering the HR "fundamentals", and (7) developing innovative partnerships with suppliers. Key challenges for the future include: (1) change management, (2) clarifying HR'S strategic role throughout the firm, and (3) attracting and retaining a diverse workforce.
Huselid, M.A., and Becker, B.E. 1999. An Interview with Mike Losey, Tony Rucci, and Dave Ulrich: Three experts respond to HRMJ's Special issue on HR strategy in five leading firms. Human Resource Management Journal, 38. (4), Winter, 353-365.
As a postscript to this HRM Special Issue on HR strategy in five leading firms, Huselid and Becker interview three preeminent experts in the field of human resources. Mike Losey is President and Chief Executive Officer of the Society for Human Resource Management (SHRM), Tony Rucci is Dean of the College of Business Administration at the University of Illinois at Chicago, and Dave Ulrich is Professor of Business at the University of Michigan.
Richard W. Beatty, Craig E. Schneier, David 0. Ulrich, Arup Varma. 1999. High Performance Work Systems: Exciting Discovery or Passing Fad? Human Resource Planning, 26-37.
Recently, several organizations reported implementing high performance work systems, with remarkable success. These HPWSs, as they are becoming known (as defined by Nadler, 1989), are primarily aimed at improving the organization's financial and operational performance. The authors conducted a survey of 39 organizations to examine the antecedents, the design, and the overall effectiveness of these initiatives. Results indicate that HPWSs that create a change in the organization's cultural behavior (e.g., cooperation, innovation) and people management practices (e.g., reward and selection systems) can positively impact the financial and operational performance of these organizations.
Becker, B.E. & Huselid, M.A. 1998. High performance work systems and firm performance: A synthesis of research and managerial implications. Research in Personnel and Human Resources Journal, 16, (1), 53-101.
This paper reviews the theoretical foundations for an HRM-firm performance relationship and focuses particularly on the potential of a high-performance work system to serve as an inimitable resource supporting the effective implementation of corporate strategy and the attainment of operational goals. Special attention is devoted to the methodological challenges inherent in the prior empirical work that has adopted this systems perspective, and what we can learn from research at different levels of analysis. Becker and Huselid summarize the evolution of their own work on the subject and present new findings that bear on the magnitude of the HRM strategy-firm performance relationship. The paper concludes by outlining several possible areas of future research and a discussion of how practitioners might implement the findings throughout their organizations.
Becker, B.E. & Huselid, M.A. Under Review. Human resources strategies, complementarities, and firm performance. July, 1998.
In this paper Becker and Huselid extend the empirical literature on this topic by examining firm performance effects of the HR system as well as the broader organizational context that supports and reinforces a high performance HR management system. They term this latter dimension of the firm's HR strategy Effectiveness and Alignment because it includes conventional notions of "fit" and contingency, but defines these contextual factors more broadly to include both senior leadership style and HR function effectiveness. This broader measure of "fit" is then compared with more conventional estimates based on interactions, including those with generic measures of corporate strategy (Porter, 1985).
Becker, B.E., Huselid, M.A., Pickus, P.S., & Spratt, M. HR as a source of shareholder value: Research and recommendations. Human Resource Management Journal, 31 (1), Spring, 1997, 39-47.
The role of the Human Resource Management (HRM) function in many organizations is at a crossroads. On one hand, the HRM function is in crisis, increasingly under fire to justify itself (Schuler, 1990: Stewart, 1996) and confronted with the very real prospect that a significant portion of its traditional responsibilities will be outsourced (Corporate Leadership Council, 1995). On the other hand, organizations have an unprecedented opportunity to refocus their HRM systems as strategic assets.
This article describes the new organizational perspective on the HRM system (shared by the CEO and the chief HR officer) necessary to transform this crisis into an opportunity. At its core, this strategic perspective requires that the CHRO be focused on identifying and solving the human capital elements of important business problems (e.g., those problems likely to impede growth, lower profitability, and diminish shareholder value). The tangible evidence of this focus is an internally coherent, externally aligned, and effectively implemented HRM system.
Huselid, M.A., & Rau, B. The Determinants of High Performance Work Systems: Cross-sectional and Longitudinal Analyses. (In progress).
This paper examines factors hypothesized to facilitate and constrain the adoption of a High Performance Work Systems (HPWS). In 2,410 firms across diverse industries and three time periods Huselid and Rau found both organizational characteristics and external environmental contingencies to be associated with the adoption of a HPWS. From the limited conceptual and empirical literature they develop a set of hypotheses, focusing not only on the correlates of the adoption of HPWS, but also on the factors associated with changes in firm deployment of HPWS across time. A large national sample of firms across three data collection periods (1992, 1994, and 1996) is then used to focus on the role of firm and environmental contingencies as predictors of HPWS adoption.
Huselid, M.A., Jackson, S.E., & Schuler, R.S. 1997. Technical and strategic human resource management effectiveness as determinants of firm performance. Academy of Management Journal, 40 (1), 171-188.
In this article, Huselid, Jackson, & Schuler improve upon the prior empirical literature on this topic by focusing on the impact of overall HRM quality on firm performance. They develop the argument that HRM effectiveness, which includes the delivery of high-quality technical and strategic HRM activities, will be reflected in valued firm-level outcomes. They then assert that two types of HRM staff capabilities will have a significant impact on the effective management of firms' human capital. To study the impact of HRM effectiveness and human resources staff capabilities on valued firm-level outcomes – employee productivity and corporate financial performance – they examine a large sample of firms drawn from a wide range of industries. Finally, two important methodological issues that could bias their results are considered: (1) the potential endogeneity of firm profitability and managerial assessments of HRM effectiveness and (2) survey response bias.
Delaney, J.T., & Huselid, M.A. 1996. The impact of human resource management practices on performance in for-profit and nonprofit organizations. Academy of Management Journal, 39, 949-969.
This study comprehensively evaluated the links between systems of High Performance Work Practices and firm performance. Results based on a national sample of nearly one thousand firms indicate that these practices have an economically and statistically significant impact on both intermediate employee outcomes (turnover and productivity) and short- and long-term measures of corporate financial performance. Support for predictions that the impact of High Performance Work Practices on firm performance is in part contingent on their interrelationships and links with competitive strategy was limited.
Huselid, M.A., & Becker, B.E. 1996. Methodological issues in cross-sectional and panel estimates of the Human Resource-firm performance link. Industrial Relations, 35, 400-422.
Because companies differ in factors such as management ability that may lead to both high performance work systems and enhanced firm performance, conventional estimates of the effects of human resource (HR) management practices on firm performance may be biased upward. Alternatively, if HR management practices are measured with error, estimates of their effects on firm performance may be biased downward. Huselid and Becker find that, although longitudinal estimates that avoid the first source of bias are substantially smaller than cross-sectional estimates, the former are strongly influenced by errors in measuring HR management practices. Based on independent estimates of the measurement error, they calculate a range of estimates that correct for both biases. They estimate that a one standard deviation increase in their measure of high performance work systems raises the market value of the corporation by approximately $15,000 per employee.
Huselid, M.A. & Becker, B.E. The Strategic Impact of High Performance Work Systems. (in progress).
This paper extends the emerging empirical literature on the firm-level impact of organizational High Performance Work Systems. Huselid and Becker's results suggest that the strategic impact of human resources (HR) on firm performance is both economically and statistically significant. The analyses validate earlier work by Huselid (1995) and extend this work with a broader measure of the HR system in a new sample of 740 publicly-held firms. Their estimates suggest that a one-standard deviation change in a firm's High Performance Work System has a per employee impact on firm market value of $38,000 - $73,000. Moreover, changes in the HR system yield substantially greater benefits when the improvements occur at either the low or the high end of the distribution.
Huselid, M.A. 1995. The impact of human resource management practices on turnover, productivity, and corporate financial performance. Academy of Management Journal, 38, 635-672.
This study comprehensively evaluates the links between systems of High Performance Work Practices and firm performance. Results based on a national sample of nearly one thousand firms indicate that these practices have an economically and statistically significant impact on both intermediate employee outcomes (turnover and productivity) and short- and long-term measures of corporate financial performance. Support for predictions that the impact of High Performance Work Practices on firm performance is in part contingent on their interrelationships and links with competitive strategy was limited.
Becker, B.E., & Huselid, M.A. 1992. Direct estimates of SDy and the implications for utility analysis. Journal of Applied Psychology, 77, 227-233. (Lead article).
Utility analysis suggests that human resources policies can have an economically significant impact on business organizations. Confidence in such conclusions, however, requires an accurate estimate of SDy. This article provides a validity check on prevailing subjective methods of SDy estimation by directly estimating SDy from unique field data. Using both simulated and field data, Becker and Huselid first illustrate the range of potential bias associated with predictor unreliability in regression analysis and show how to calculate corrected values. They then discuss the methodological problems of directly estimating SDy with organizational data and provide a range of estimates for SDy. Their direct estimation of SDy yields values ranging from 74% to 100% of mean salary, which are considerably greater than conventional subjective judgments.
Becker, B.E., & Huselid, M.A. 1992. The incentive effects of tournament compensation systems. Administrative Science Quarterly, 37, 336-350.
Tournament models have developed into an important component of the theoretical literature on organizational reward systems. However, with one exception there have been no empirical tests of the incentive effects of tournament models in a field setting. Drawing on a panel data set from auto racing, Becker and Huselid show that the tournament spread (prize differential) does have incentive effects on both individual performance and driver safety, that these effects peak at higher spreads, and that controlling for the dollar value of the tournament spread, the prize distribution has little influence on individual performance.
Beatty, R.W., & Ulrich, D.O. 1991. Re-Energizing the Mature Organization. Organizational Dynamics, American Management Association, 16-30.
Traditional ways of competing have reached a level of parity in which businesses cannot easily distinguish themselves solely on the basis of technology, product, or price. The ability of an organization to conceptualize and manage change – to compete from the inside out by increasing its capacity for change – may represent that novel way to compete.
Beatty and Ulrich argue that this need to understand and manage change is particularly salient for mature firms where the long-established norms of stability and security must be replaced with new values such as speed, simplicity, unparalleled customer service, and a self-confident, self-reliant workforce. The authors explore how mature firms can be re-energized and describe the unique challenges of creating change in mature firms – detailing principles that can be used to guide change and identifying the leadership and work activities required to accomplish change.
Huselid, M.A., & Day, N.E. 1991. Organizational commitment, job involvement, and turnover: A substantive and methodological analysis. Journal of Applied Psychology, 76, 380-391.
This study examines the hypothesis that organizational commitment and job involvement interact in the prediction of turnover (Blau & Boal, 1987). Prior work in this area has not incorporated a sufficiently broad definition of commitment, has omitted relevant covariates, and has utilized inappropriate estimation procedures (ordinary least-squares regression [OLS]). The presence of a commitment, involvement interaction was tested in three estimation models with data obtained from 138 supervisors. Models estimated with OLS replicated prior work (Blau & Boal, 1989) irrespective of whether additional covariates were included. Identical models estimated with logistic regression provided no support for the presence of a commitment, involvement interaction. Huselid and Day conclude that results obtained with linear techniques are a function of an inappropriate estimation procedure when the dependent variable is binary. The potential impact of the widespread use of linear estimation procedures in turnover research is discussed.
SHRM Empirical Study 1995 – 2003This table provides a summary and comparison of 158 empirical studies linking HRM systems with firm performance published between 1995 and 2003. Included in the table are the citation, level of analysis, sample, HPWS indicator, performance indicator, presence of main effect, presence of interaction, and effect size.
SHRM Study References 1995 – 2003This file provides the complete references to the 158 studies included in the table described above.
2003 – present