U5

Working Capital Management

Using the article by Pasandideh and Darabi (2015) assigned in this unit, “The Effect of Working Capital Strategies on Performance Evaluation Criteria,” discuss the importance of effective working capital management, its role in meeting the firm’s strategic objectives, and its effect in value creation. Be sure to provide examples of metrics used to evaluate working capital management and discuss how these metrics should be interpreted. Provide support for your discussion.

AsianSocial Science; Vol. 11, No. 23; 2015

ISSN 1911-2017 E-ISSN 1911-2025

Published by Canadian Center of Science and Education

59

The Effect of Working Capital Strategies on Performance Evaluation
Criteria

Ali Kourosh Pasandideh1 & Roya Darabi2

1 Accounting, Islamic Azad University, South Tehran Branch, Tehran, Iran
2 Department of Accounting, Islamic Azad University, South Tehran Branch, Tehran, Iran

Correspondence: Roya Darabi, Department of Accounting, Islamic Azad University, South Tehran Branch, Tehran,
Iran. E-mail: royadarabi110@yahoo.com

Received: June 21, 2015 Accepted: August 29, 2015 Online Published: September 17, 2015

doi:10.5539/ass.v11n23p59 URL: http://dx.doi.org/10.5539/ass.v11n23p59

Abstract
The main aim of the present study is to explore the effect of working capital strategies on performance
evaluation criteria. To this end, a number of 658 companies were selected during the period of 2007. For testing
research hypotheses, multivariate linear regression statistical technique was used. The results indicate that
investment strategies have a significant effect on return on assets and Tobin Q indicator. However, these
strategies do not have any significant effect on Market Value Added. Financing strategies also have only a
significant effect on Return on Assets.

Keywords: working capital strategies, investment strategies, financing strategies, return on assets, Tobin q
indicator, market value added

1. Introduction
Working capital management is one of the most important issues that business unites managers are facing and it
plays a significant role in growth and survival of a company. Working capital management is the management of
current assets such as cash, short-term investment, accounts receivable and balance and current liabilities of
business units (Reza Zadeh & Heidarian, 2010). Due to a number of reasons, working capital management is
necessary for financial health of business units. First, if the funds invested in working capital, it will be
inharmonious, in comparison to total assets of the company, and it is possible that these funds have not been used
in an efficient situation. Efficiency in working capital management is of great importance, especially in
manufacturing companies. In other words, a good and systematic management of working capital leads to
increased market value of the business unit and efficient management of working capital can lead to fundamental
outcomes and ignoring it can be dangerous for any company. Second, working capital management directly
affects liquidity and profitability of business units and also their net value (Izadinia & Taki, 2010). On the other
hand, mangers in companies expect to make a significant effect on company’s profitability with the use of
working capital management. Therefore, for many companies, working capital management can be one of the
most important topics n financial management (Dong & Su, 2010), which plays an important role in managerial
structure of an organization and has a great importance in achieving Great economic gains as a main driving
force in moving organizations forward (Jannesari, 2012).

Companies, considering the relative benefits of the two major strategies of working capital management
including aggressive and conservative strategies, can select one of these strategies. By choosing the aggressive
strategy, investment in working capital components is kept at the minimum possible level and by choosing the
conservative strategy, a company can only think about increasing its sales and are not concerned about
proportion of investment in working capital with profitability (Samson et al., 2012). In other words, it can
increase the power of liquidity. By minimizing investment in working capital (aggressive strategy), a positive
effect can be created on company’s profitability and in this way total assets and proportionally net current assets
can be reduced. Of course, if companies reduce the level of their inventory levels of materials and goods overly,
it is so much likely for them to lose their customers. Or if they will not pay their accounts payable on time, they
might lose the corresponding cash discounts that in some cases, and the cost of lost opportunity related to these
cases is considerable (Mwalla, 2012).

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Hence, it is necessary for managers to consider these matters at the time of selecting aggressive strategy.
Selection of conservative strategy and high investment in working capital can decrease profitability. For example,
although keeping materials and goods inventory at a high level, it leads to reduced loss due to shortage of raw
material and a halt in production line; however, fluctuations in material prices and losing customers are resulted
from lack of having goods to supply (Malekian & Asghari, 2011). However, the return resulting from, generally,
is only equal to inflation rate. Also, choosing aggressive strategy with regard to granting credit to customers
increases sales, because, on one hand, it is considered as a king of price reduction and encourages customers to
make their purchases even at periods of recession and on the other hand, it enhances the relationship between the
company and its customers in the long run (Saghir et al., 2011).

In order to manage working capital affairs of a business unit, there are a variety of strategies from which,
working capital management of a business unit, should find a proper balance between current assets and current
liabilities and secondly , in different situations, considering external and internal factors of a unit for profit and
also considering the risk and return should select appropriate strategies for their working capital management in
order to be able to efficiently manage current assets and liabilities, enhance company’s performance and
maximize shareholders’ wealth (Padachi, 2006).

Therefore, mangers in companies are expected to be able to make a significant effect on the profitability of their
companies through selecting appropriate working capital strategies as a considerable part of the resources of
companies is invested in working capital, which in turn increases the importance of working capital
management.

Based on actual information and relevant previous conducted studies, selecting the type of working capital
strategies can get useful data for predicting the performance of companies and can play an important role in
investors’ decision-making and other users of financial statements with regard to stock trade. Hence, in line with
the work of previous researchers, this study seeks to analyze and explore whether working capital strategies are
effective on performance evaluation criteria in the companies listed on Tehran Stock Exchange. Visual form of
the relationships between research variables is presented in the following conceptual research model:

Figure 1. Research conceptual model

2. Research Hypotheses and Related Models
Hypothesis 1: Working capital strategies have a significant effect on accounting performance criteria.

Hypothesis 2: Working capital strategies have a significant effect on combined performance criteria (accounting
and economic).

Hypothesis 3: Working capital strategies have a significant effect on economic performance criteria.

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In this study, for testing research hypotheses, the following models are used:

(1) ROA = β0 + β1 Investment of Strategy +β2 Financing of Strategy + β 3 Size + β 4 Growth + β5 Lvrg + β 6 Gdogr + ɛ
(2) QTobin = β0 + β1 Investment of Strategy +β2 Financing of Strategy + β3 Size + β4 Growth + β5 Lvrg + β6 Gdogr + ɛ
(3) MVA= β0 + β1 Investment of Strategy +β2 Financing of Strategy + β 3 Size + β 4 Growth + β5 Lvrg + β 6 Gdogr + ɛ
In the above models:

ROA = Return on assets

Investment of strategy = Investment strategy

Dummy variables: for companies having conservative strategy, a value of 1 and for companies having
aggressive strategy, a value of 0 is considered.

Financing strategy: Financing strategy

Size: Company size

Growth: Sales growth

Lvrg: Financial leverage

Gdogr: Economic growth of the country

QTobin: Tobin Q indicator

MVA: Market value added ɛ: Residual of the model
3. Research Method
The present study is correlational and based on type, its Ex post facto research design. In other words, it is
conducted based on analyzing past data (financial statements of companies). Also, the data used in this study are
panel data because research variables are both measured and studied among various companies as well as during
the time period of this study. In terms of objective, this study is an applied research and in terms of data
collection method, it is a bibliographical research. In fact, the researcher has collected the required information
and data with exploring available documents and sources in official website of Tehran Stock Exchange
Organization and after studying them and performing necessary tests, have interpreted the findings and reported
the obtained results.

3.1 Research Population and Sampling Method

Research population of the present study includes all companies listed on Tehran Stock Exchange during the
time span of 2007-2013. Purposeful sampling was used for this study; which means that research population
were filtered by considering a number of conditions and companies having these conditions were analyzed as
sample companies. The conditions applied for selecting research sample are presented below:

 Companies being present in Stock Exchange for the total length of research time period.
 Companies whose fiscal year has not changed during research time period.
 Companies whose stock was traded during research time period.
 Companies that are not among investment or financial intermediary companies.
By applying the above mentioned conditions, 94 companies were selected as the main sample.

3.2 Data Collection Method and Tools

In the present study, in order to collect the information related to theoretical principles and research background,
bibliographical method was used. Research data also have been collected with the use of Rah Avard Novin
software and in the event of lack of availability of information in this database, records of financial statements
available in the library of Tehran Stock Exchange organization have been used.

4. Results and Discussion
Descriptive indicators of research variables were presented in Table 1.

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Table 1. Measures of central tendency and dispersion for each of research variables

Indicators
Return on
assets

Q Tobin
Market
value
added

Investment
strategies

Financing
strategies

Size
Sales
growth

Leverage GDP

Average 0.121910 0.861719 639455.9 0.557078 0.465753 13.16267 0.237903 2.051037 1.963927

Mean 0.101661 0.808676 608721.5 1.000000 0.000000 13.12107 0.187571 1.706616 3.160000

Max. 0.426784 1.395740 8.917633 1.000000 1.000000 17.63089 1.338152 4.219150 7.840000

Min. -0.339995 0.133315 -1.181768 0.000000 0.000000 9.880833 0.435169- 1.163268- -5.400000

Standard
deviation

0.139977 0.229006 194168.9 0.497110 0.499206 1.231684 0.335615 1.585031 4.307258

Skewness 0.265884 0.191350 0.818789 -0.229813 0.137309 0.378189 0.936852 0.14979 0.327552-

Kurtosis 3.244205 3.426912 3.810943 1.052814 1.018854 3.140533 4.695355 3.504925 2.004309

Total 80.09510 566.1491 +084.20 366.0000 306.0000 8647.873 156.3021 1347.531 1290.300

Number of
observations

658 658 658 658 658 658 658 658 658

In order to study the normality distribution of data in econometric research, Jarque-Bera test is used. Table 2
indicates the results.

Table 2. Results of Jarque-Bera test

Normality
test

Return of
assets

Q Tobin
Market
value
added
Investment
strategies

Financing
strategies

size
Sales
growth

Leverage GDP

Jarque-Bera 4.158341 4.385334 5.245521 109.5764 109.5097 2.624863 3.745892 5.180147 38.88788

Probability 0.091245 0.089524 0.065234 0.000000 0.000000 0.265258 0.125284 0.072455 0.000000

Number of
observations

658 658 658 658 658 658 658 658 658

Results of Jarque-Bera test indicate that probability value (Jarque-Bera) for the variables including return of
assets, Q Tobin, market value added, size, sales growth and leverage is larger than 0.05. Therefore, the null
hypothesis is not rejected and with a 95% confidence, it can be said that these variables have a normal
distribution. However, for investment strategies, financing strategies and also GDP of this value is smaller than
5%, and it means that these variables are not normal. In the following, research hypotheses are tested:
Hypothesis 1: working capital strategies have a significant effect on accounting performance criteria.
Estimation method of the present model is based on panel data method. This method is a combination of “Time
series data” and “cross-sectional data”. In each of the time series models and cross-sectional data, there are some
shortcomings which can be mitigated in panel data model. In panel data method, two Chow and Hausman tests
are used for determining one of the methods of fixed effects or random effects and the results of these two tests
have been presented in the below Tables.

Table 3. Results of chow test for 1st hypothesis

Description p-value Freedom degree Probability

Cross-section F 11.048175 (557,93) .0000

Cross-section Chi-square 686.858359 92 .0000

As it is evident form the above table, the results of Chow test indicate that the obtained probability for F-test is
smaller than 5%. Therefore, for testing this hypothesis, Panel data should be used.

Table 4. Results of Hausman test for 1st hypothesis

Description p-value Freedom degree Probability

Cross-section F 20.604381 6 0.0022

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Since, the probability obtained for Hausman test is smaller than 5%, fixed effects model is selected and finally,
the model is estimated with the used of fixed effects model.

Table 5. Regression test for 1st hypothesis

Variable Coefficient of determination Estimate deviation t-value Sig. level

Constant 0.301449- 0.138953 2.169428- 0.03*

Investment strategies 0.046527 0.009184 5.065889 .000**

Financing strategies 0.065118- 0.010607 6.139289- .000**

Size 0.031249 0.010505 2.974717 0.003**

Sales growth 0.079340 0.013747 5.771434 .000**

Leverage 0.0011955- 0.001582 1.235439- 0.217

GDP 0.000804 0.000857 0.938043 0.348

* p< .01,

** p< .005

Considering the obtained significance levels for variables being studied in 1st hypothesis, results can be
described as below:

• For the 1st secondary hypothesis, due to the fact that the obtained significance level is smaller than 5% (0.000),
the null hypothesis is rejected and with 95% confidence level, it can be concluded that investment strategies have
a significant effect on return on assets.

• For 2nd secondary hypothesis, due to the fact that the obtained significance level is smaller than 5% (0.000),
therefore, the null hypothesis is rejected and with 95% confidence level, it can be claimed that financing
strategies have a significant effect on return on assets.

Table 6. Justification and significance of the whole model

R
Durbin-Watson

ANOVA

Coefficient of determination Adjusted coefficient of determination F Sig.

0.751094 0.706854 1.742631 16.97773 0.000

** p< .005 Considering table 6, since the value of Durbin-Watson test is located in the range of 1.5 to 2.5, the hypothesis indicating to lack of existence of correlation between errors is not rejected and therefore, regression test can be used. Considering that the F-test values (16.97773) is significant at the level smaller than 0.01, it can be concluded that regression model of the present study, a combination of independent, control and dependent variables, is a good model and that independent and control variables together have the ability to explain changes in dependent variable. Hypothesis 2: working capital strategies have a significant effect on combined performance (accounting and economic) criteria. Results of the two Chow and Hausman are presented in the below tables. Table 7. Results of chow test for 1st hypothesis

Description p-value Freedom degree Probability

Cross-section F 8.851340 (557,93) .0000

Cross-section Chi-square 596.161840 93 .0000

As it is clear from the above table, Chow test results indicate that the obtained probability for F-test is smaller
than 5%. Therefore, for testing this hypothesis, panel data should be used.

Table 8. Results of Hausman test for 2nd hypothesis

Description p-value Freedom degree Probability

Cross-section F 62.3422340 6 .0000

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Since, the probability obtained for Hausman test is smaller than 5%, H0 hypothesis of Hausman test is rejected
and for estimating the parameters of multivariate regression equations fixed effects model should be used.

Table 9. Regression test for 2nd hypothesis

Variable Coefficient of determination Estimate deviation t-value Sig. level

Constant 3.657586- 2.116712 1.727956- 0.084

Investment strategies 0.230263 0.028942 7.956132 0.000**

Financing strategies 049010- 0.056718 0.864093- 0.387

Size 0.335796 0.1611735 2.076216 0.038*

Sales growth 0.225837 0.025176 8.970365 .000**

Leverage 0.031677- 0.006907 4.586239- .000**

GDP 0.002612 0.011141 0.234443 0.814

* p< .01, ** p< .005

Considering the obtained significance levels for variables being studied in 2nd hypothesis, results can be
described as below:

• For the 1st secondary hypothesis, due to the fact that the obtained significance level is smaller than 5% (0.000),
therefore, the null hypothesis is rejected and with 95% confidence level it can be stated that investment strategies
have a significant effect on Q Tobin indicator.

• For 2nd secondary hypothesis, due to the fact that the obtained significance level is larger than 5% (0.3879),
therefore, the null hypothesis is accepted and with 95% confidence level, it can be stated that financing strategies
do not have a significant effect on Q Tobin indicator.

Table 10. Justification and significance of the whole model

R
Durbin-Watson
ANOVA
Coefficient of determination Adjusted coefficient of determination F Sig.

0.672312 0.614069 1.747979 11.54330 .000

** p< .005 Considering table 10, since the value of Durbin-Watson test is located in the range of 1.5 to 2.5, the hypothesis indicating the lack of correlation between errors is not rejected and therefore, regression test can be used. Considering the fact that the f-test values (11.54330) is significant at error level smaller than 0.01, it can be concluded that regression model of the present study , a combination of independent, control and dependent variables, is a good model and that independent and control variables together have the ability to explain changes in dependent variable. Hypothesis 3: working capital strategies have a significant effect on economic performance criteria. Results of the two Chow and Hausman are presented in the below tables. Table 11. Results of chow test for 3rd hypothesis

Description p-value Freedom degree Probability

Cross-section F 25.713510 (557,93) .0000

Cross-section Chi-square 1094.849704 93 .0000

As it is clear from the above table, Chow test results indicate that the obtained probability for F-test is smaller
than 5%. Therefore, for testing this hypothesis, panel data should be used.

Table 12. Results of Hausman test for 3rd hypothesis

Description p-value Freedom degree Probability

Cross-section F 16.406648 6 0.0117

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Since, the probability obtained for Hausman test is smaller than 5%, H0 hypothesis of Hausman test is rejected
and for estimating the parameters of multivariate regression equations fixed effects model should be used.

Table 13. Regression test for 3rd hypothesis

Variable Coefficient of determination Estimate deviation t-value Sig. level

Constant 10264.51- 0.288519 3.557583- 0.004**

Investment strategies 161421.7 11117107 1.452004 0.147

Financing strategies 13932.55 49519.46 0.281355 0.778

Size 819899.8 217031.7 3.777788 0.002**

Sales growth 17996.6 43582.10 4.125469 0.000**

Leverage 25957.12- 7942.620 3.268080- 0.001**

GDP 12978.45 8682.854 1.494721 0.135

* p< .01, ** p< .005

Considering the obtained significance levels for variables being studied in 3th hypothesis, results can be
described as below:

• For the 1st secondary hypothesis, due to the fact that the obtained significance level is larger than 5% (0.1471),
therefore, the null hypothesis is accepted and with 95% confidence level, it is concluded that investment
strategies don’t have a significant effect on market value added.

• For 2nd secondary hypothesis, due to the fact that the obtained significance level is larger than 5% (0.7785),
therefore, the null hypothesis is accepted and with 95% confidence level, it can be stated that financing strategies
do not have a significant effect on market value added.

Table 14. Justification and significance of the whole model

R
Durbin-Watson
ANOVA
Coefficient of determination Adjusted coefficient of determination F Sig.

0.883244 0.862492 1.527839 42.56184 .000

** p< .005

Considering table 14, since the value of Durbin-Watson test is located in the range of 1.5 to 2.5, the hypothesis
indicating the lack of correlation between errors is not rejected and therefore, regression test can be used.
Considering the fact that the F-test values (42.56184) is significant, it can be concluded that regression model of
the present study, a combination of independent, control and dependent variables, is a good model and that
independent and control variables together have the ability to explain changes in dependent variable.

5. Conclusion
Nowadays, the application of financial management topics has gained a special place in the enhancement of the
efficiency of an organization. Hence, making financing and investment decisions as the two main responsibility
of financial mangers is of great importance. To this end, working capital management, that is, management of
resources and current expenses, has gained a great deal of importance for maximizing shareholders’ wealth as a
part of The area of financial management topics (Rahman & Nasr, 2007). Mangers of units for profit in different
situations considering the internal and external factors and also considering risk and return should select a proper
strategy for managing the working capital of their unit. If the strategy type of the management of current assets
and liabilities is selected properly in a given time, it will make possible the achievement of the best working
capital management strategy (Michalski, 2003). Striking a balance in current assets and current liabilities is of
great importance, in a way that decision-making about one will affect the other greatly (Jahankhani & Talebi,
1999).

In managing affairs related to working capital of a business unit, there are various strategies, resulting from
combining current assets strategy and current liabilities strategy (Reymond, 2001). Working capital management
of a business unit in different conditions should select appropriate strategies for a company so that it can manage

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current assets and liabilities efficiently. Currently, most of those who are involved in industries of our country
have understood the importance of working capital, however, they are still searching more for external and
temporary solutions for solving the existing problems. In other words, they see the solution in granting cheap and
sufficient loans to companies, while, with making a proper use of working capital and making the corresponding
policies, with the help of internal solutions liquidity can be improved and initial capitals can be supported
(Rahnamay-e Roudposhti & Kiaee, 2009).

On the other hand, with the separation of management from ownership and following that, with the emergence of
agency theory, performance evaluation has been raised as one of the most important topics in accounting.
Evaluation and performance of companies have always attracted the attention of shareholders, investors,
financial creditors, such as banks and financial institutes, Creditors and specially managers (Mahdavi &
Ghorbani, 2012). One of the effective factors on performance evaluation criteria is working capital strategies.

In the presents study, the effect of working capital strategies on performance evaluation criteria in Tehran Stock
Exchange has been explores and results indicate that investment strategies have a significant effect on return on
assets and Q Tobin indicator, however, they don’t have any significant effect on market value added. Financing
strategies, also are only having a significant effect on return on assets.

Based on the obtained results from the present research, the following recommendations are presented:

Considering the effect of investment strategies on return on assets and Q Tobin indicator, companies in this study
are recommended to increase their return on investment to some extent with selecting aggressive strategies,
although it should be noted that aggressive working capital strategies at the same time increases the risk of
default and companies should make their working capital strategies in a way to strike a balance in risk and return
which is the foundation of all financial decisions.

Considering the effect of financing strategies on return on assets, companies in this study are recommended to
establish and apply appropriate strategies with regards to financing method and current liabilities management in
order to reduce their Cost of debt and make use of financial leverages. As an example, diversification of
financing methods and the use of methods such as credit in current account, issuing bonds and moving toward
using securities for supporting mortgage can be mentioned.

For a larger effect of working capital management strategies on the performance of companies, it is
recommended that companies considering the General atmosphere of the industry they are working in, make
some initiatives in some areas such as pricing of products, responding to potential demands and consideration of
similar industries, which in turn require strategic and long-term planning in these companies.

References
Dong, H. P., & Su, J. (2010). The Relationship between Working Capital Management and Profitability: A

Vietnam Case. International Research Journal of Finance and Economics, 49(1), 59-67.

Izadinia, N., & Taki, A. (2010). Studying the effect of working capital management on profitability potential of
companies listed on Tehran Stock Exchange. Financial Accounting, 2(5), 120-139.

Jahankhani, A., & Talebi, M. (1999). A Review and critique of different liquidity indicators in companies.
Financial Studies, 4(13), 6-31.

Jannesari, S. A. (2012). The impact of working capital management on profitability of small and medium sized
business units. Journal of Auditor, 58.

Mahdavi, Gh., & Ghorbani, A. (2012). A comparative study of the role of new and traditional indicators of
liquidity for financial performance evaluation of companies listed on Tehran Stock Exchange. Journal of
Financial Accounting Studies, 4(1), 67-88.

Malekian, E., & Asghari, J. (2006). Studying the relationship between economic value added and rate of return
on assets for performance evaluation of companies listed on Tehran Stock Exchange. Exchange, 54-55.

Michalski, G. (2003). Small and Medium Enterprises Accounts Receivable Management with Value of Liquidity
in View. Finansowe Aspekty Funkcjonowania Malych i Srednich Przedsiebiorstw, 357-369.

Mwalla, M. A. (2012). The Impact of Working Capital Management Policies on Firm’s Profitability and Value:
The Case of Jordan. International Research Journal of Finance and Economics, 85(4), 1450-2887.

Padachi, K. (2006). Trends in Working Capital Management and its impact on firm performance: An analysis of
Mauritan small manufacturing firms. International Review of Business Research Papers, 2(1), 45-56.

Raheman, A., & Nasr, M. (2007). Working Capital Management and Profitability-Case of Pakistani Firms.

www.ccsenet.org/ass Asian Social Science Vol. 11, No. 23; 2015

67

International Review of Business Research Papers, 3(2), 275-296.

Rahnamay-eRoudposhti, F., & Kiaee, A. (2009). Studying and explaining working capital management strategies
in companies listed on Tehran Stock Exchange. Journal of Accounting Knowledge and Research, 13.

Reymond, P., & Novo. (2001). Financial management. Tehran: SAMT publications.

Reza Zadeh, J., & Heidarian, J. (2010). The effect of working capital management on profitability of Iranian
companies. Accounting Studies, 2(7), 20-23.

Saghir, A., Hashmi, F. M., & Hussain, M. N. (2011). Working capital management and profitability: Evidence
from Pakistan firms. Interdisciplinary Journal of Contemporary Research in Business, 3(8), 1092-1105.

Samson, A. A., Mary, J., & Erekpitan, I. O. (2012). The impact of working capital management on the
profitability of small and medium scale enterprises in Nigeria. Research Journal of Business Management,
5(2), 23-39. http://dx.doi.org/10.3923/rjbm.2012.61.69

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