HOW TO MEASURE SUSTAINABILITY OF SUPPLY CHAIN.

1. Abdelmalek Essaâdi University, Faculty of Sciences and Techniques ,Tangier, Morocco. 2. Research team: Materials, Environment and Sustainable Development. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History

Earlier firms mainly based on financial performance to assess their progress. Thenceforth, maturity of supply chain must be evaluated from a more comprehensive performance including, economic, environmental and social dimensions. The purpose of this paper is on consideration of how to use indicators to monitor sustainable development in supply chain. Integrated information on sustainable development of a supply chain is very essential for decision-making since it is very difficult to evaluate the performance of the supply chain on the ground of too many indicators. The objective of this work is to design a mathematical module for obtaining a global composite index (Ig) in order to track integrated information on economic, environmental, social and global performance of the supply chain with time. Normalized indicators were associated into three sustainability sub-indices and finally composed into a global indicator of a supply chain performance. A case study was used to validate this module for one year (2016), interpretation of results is given and the utility of Ig with its relevance is pointed out.

Introduction:
The main objective in supply chains management was to improve industrial competitiveness by minimizing costs, providing level of service required by customer, effectively allocating activities on actors of production, distribution and transport. Currently, supply chains must integrate two new dimensions in their performance: their impact on society and on environment. Supply chains must develop methods and approaches to consider and measure their impacts on economic, environmental and social levels and analyze interactions between these impacts.
Traditional mechanisms for performance measurement, such as costs, do not give supply chains a clear view on consequences of their management practices. Approaches available today are mainly focused on environmental sphere, when the reality of impacts of supply chain management practices is more complex, integrating the three dimensions of sustainable development (economic, environmental and social). It's true that public institutions encourage firms to make sustainable development a strategic issue. In supply chain, sustainable development is a transversal concept that affects all stakeholders who have different and sometimes conflicting goals. Performance is complex to master given different processes to consider, various stakeholders to integrate and various dimensions in which stakes are declined. To take into account all supply chains impacts, it is essential to develop a comprehensive performance evaluation method. These methods must be consistent with specificities of each stakeholder. The

Proposal of A Module to Measure Global Performance of Supply Chains:
To measure global performance of supply chain, and thus facilitate decision making, we propose an analytical evaluation module. We propose to characterize each dimension of sustainable development by a number of indicators (Table 1).
We based our selection of indicators on the three recommended requirements by (Roy, 1985) [13]:  Completeness: we must not it has too few indicators; otherwise, it means that some assessment elements were not taken into account.  Non-redundant: it should not be some indicators that are duplicated, thus more than necessary.  Consistency: global preferences (all indicators) are consistent with local preferences (for a single indicator).

Correlation of Global Performance Indicators with Supply Chain Decisions:
We analyze the possible correlations between selected sustainable development indicators and the decision variables of the mathematical module, to build mathematical expressions which formalizes and measures the value of these indicators. Thus the performance evaluation is operationalized so consistently.  The analysis of this inventory highlights five main criteria, which are reliability, reactivity, flexibility, quality and financial performance and nine indicators (Table 3). The total cost of supply chain (T C ) is calculated as follow ((Equation (1)): we can define an environmental impact as a change in the environment, due to the intervention known or suspected of man, direct or indirect, that could have a potentially adverse effect (from simple nuisance to destruction) on lasting quality the natural environment and ecosystems, and consequently, on human health. Decisions and activities of firms have an impact on the natural environment, regardless of the implantation site thereof. These impacts can be associated with the use of biological and non-organic resources by the company, with the generation of pollution and wastes and with the impact of its activities (products / services) on natural habitats. So to reduce their environmental impact, it is that companies adopt an integrated approach that takes into account the wider implications of their decisions and activities from an environmental point of view. The inventory analysis of environmental criteria met in the very abundant literature allows us to isolate three environmental criteria, which are environmental management, use of resources and pollution and nine indicators (Table 4). 407 b i : environmental budget of entity i c i : number of environmental certifications of entity i ei: energy consumed by entity i; e ij : energy consumed by moving between entity i and residence of employees j; e kl : energy consumed by moving between entity k and entity l; e j : quantityt of water consumed by entity j m j : quantity of raw materials consumed by entity j pl j : quantity of liquid pollutants generated by entity j ps j : quantity of solid pollutants generated by entity j g i : amount of greenhouse gases generated by entity i g ij : amount of greenhouse gases generated by the movement between entity i and residence of employees j; g kl : amount of greenhouse gas generated by the movement between entity k and entity l; p di : number of decibels generated by entity i; p dij : number of decibels generated by the movement between entity i and residence of employees j; p dkl : number of decibels generated by the displacement between entity k and entity l; Social Performance of supply chain: Social responsibility also led to evaluate social performance. It measures the social consequences of the company's activity for all of its stakeholders who are mainly employees (working conditions, remuneration level, no discrimination, ...), suppliers, customers (security and psychological impacts of products), local communities (nuisances, respect of cultures) and society in general. The analysis of the inventory of social criteria found in the recent literature allows us to isolate five social criteria, which are labor rights, working conditions, health and safety, community involvement and consumersand twenty indicators (Table 5):

Global Performance of Supply Chain:
We specified in tables 3, 4 and 5 indicators respectively measuring the goals of economic, environmental and social performance of supply chain. To measure the global performance of supply chain and thus facilitate decision making, indicators should be aggregated into a single index (I g ). The aggregation is done at two levels: 1. Aggregation of indicators within each dimension of sustainable development. We obtain three sub-indices that measure each one economic, environmental and social performance of supply chain. 2. Aggregation of the three sub-indices of sustainable development. We then get the global composite index which measures the global performance of supply chain.
When aggregating we face two difficulties. The first concerns the heterogeneity of units of indicators measurement, hence the need to normalize thereof. The second touch to inequality of indicators importance, suggesting weighted indicators to express their relative importance. To do this, we use the principle of weighting of AHP method [15], which was used to calculate the composite index of sustainable performance [16], [17].
We propose an aggregation of indicators as follows: For each j {Eco, Env, Soc}, we build a matrix = ( x ) where indicators of each j dimension are compared 2 by 2 by the decision maker. The comparisons are made by posing the question which of two indicators i and i' is more important. The intensity of preference is expressed on a factor scale from 1 to 9 (Table 6). Table 6: Comparison scale of AHP method [18].
The value of 1 indicates equality between the two indicators while a preference of 9 indicates that one indicator is nine times more important than the one which it is being compared. This scale was chosen, because in this way comparisons are being made within a limited range where perception is sensitive enough to make a distinction. In the matrix A j , if indicator i is "p-times" the importance of indicator i', then necessarily, indicator i' is "1/p-times" the importance of indicator i, where the diagonal and reciprocal property ( )

Weight of indicators i is given by the formula:
∑ ∑ One disadvantage of AHP method outlined in literature [19] is the problem of intransitivity preferences. Indeed, pair wise comparison may lead to the non-transitivity that cannot be removed as part of AHP method.
However, perfect consistency rarely occurs in practice. In AHP method the pair wise comparisons in a judgment matrix are considered to be adequately consistent if the corresponding consistency ratio (CR) is less than 10% [15]: CR should not exceed the value of 0.05 if Aj is (3 x 3), 0.08 if the matrix is (4 x 4) and 0.1 if the matrix is greater than or equal to (5 x 5) [20].
CR coefficient is calculated as follows: first a consistency index (CI) needs to be estimated. This is done by adding the columns in the judgment matrix and multiply the resulting vector by the vector of priorities (i.e., the approximated eigenvector) obtained earlier. This yields an approximation of the maximum eigenvalue, denoted by . Then, CI value is calculated by using the formula: Next, CR is obtained by dividing CI by random consistency index (RI) as given in table 7. Otherwise matrix A should be evaluated: Preference factor, p Importance definition 1 Equal importance 3 Moderate importance of one over another 5 Strong or essential importance of one over another 7 Very strong or demonstrated importance of one over another 9 Extreme importance of one over another 2,4,6, : the performance of dimension j of sustainable development of supply chain is good in period t;  Step 5: weighting of sub-indices using AHP method (same principle as in step 3). : the global performance of supply chain is good in period t; By comparing the value of global composite index calculated with desired goal (value 1), we get the level reached ((+) or (-)) for the global performance of supply chain.
We summarize the method of calculating the composite index of global performance which is divided into several parts in the Fig. 1.   Fig. 1: calculation procedure of I g Application: The reliability of the proposed module has been tested in a case study. We chose an automotive supply chain installed in north of Morocco (Tangier), which its principal business activity is electrical harnesses for cars. Achieving the leadership of its branch is therefore a core principle at the supply chain. Needed data have been obtained from General Management team. This supply chain is constituted of: o Three production sites (in Tangier) o Eight suppliers (in Tangier) o Three customer (In United Kingdom, France and United States) To evaluate global performance of this supply chain, our proposed module was applied to the case chain and was delivered for 2016.
Compute of Economic Performance: Table 8: Normalized economic indicators of the case supply chain. Table 9: weights of economic indicators of the case supply chain.

Compute of Global Performance:
Equal weights (1/3) have been attributed to each sub-index to derive (I g ). Certainly, other methods of weighting the sub-indices of (I g ) could be applied, for example by using public opinion polls or involving expert judgment. However, which makes equal weighting a sensible option. Finally, we find global composite index (I g ), based on the following equation: Interpretation of Results: 9 economic, 9 environmental and 20 social indicators were aggregated into sustainable sub-indices for a case supply chain and finally aggregated into the I g . The values of sustainable sub-indices and the I g for the case supply chain over 2016 year are graphically presented in Fig. 2.  That is very important since nowadays a great emphasis have been put on the economic assessments and less on the social and environmental one. Environmental performance of the case supply chain has a value of 14.50% which is a very bad performance that is to say this supply chain has a very negative impact on the environment. As the economic performance, social performance achieved a verge good value (80.90%), thing which reflect the respect of social side by this supply chain. Taking into consideration these three performances, this supply chain achieved a good global performance (61.40%) which must be improved in the coming years especially through the improvement of environmental performance.

Discussion and Contribution of Our Module:
The purpose of (I g ) is to give both a simplified and quantified expression for a more complex composition of several indicators. It can be used to inform decision-makers of development trends in supply chain. However, it may also be included in a more targeted context, such as reflecting the status of supply chain regarding sustainability, providing information to critical decision processes, or possibly forming the basis for a supply chain to head in a certain direction. This evaluation module helps to highlight opportunities for improvement and where best practices might be found. It provides early warning information and tracks sustainability of supply chain. Decision-makers could easily interpret (I g ) and its corresponding sub-indices than trying to find a trend in many separate criteria of sustainable development. If included in the annual sustainability report, we could use this module to present the progress of supply chain in terms of sustainability to various parties interested in supply chain sustainability. Also, this evaluation module if would be applied to different supply chains, it would be possible to compare and rank them in terms of sustainability.
Based on our evaluation module of global performance we can decide if we apply or not a given best practice in supply chain following its sustainable performance calculated by (I Eco , I Env , I Soc and Ig). By this module, we provide to decision maker a tool which allows him:  To analyze the current and potential value of activities implemented and to consider actions to strengthen this value such as the implementation of sustainable best practices. This analysis allows him to define the scope of activities and to consider several options for this end, as part of differentiation strategy by CSR.  To analyze the profile of the global performance related to supply chain decisions during the planning phase, choose the configuration of the chain and the way to exploit it in advanced and optimized manner in order to ensure target level of global performance. This later defines the strategy or CSR policy that the decision maker wishes to implement.  To know precisely the additional investment in terms monetary, which he must engage to achieve the level of global performance desired.  And finally, to have quantitative performance indicator which used to control the supply chain and for the purposes of communication.

Conclusion:-
The purpose of this paper is to show the difficulties in measuring global performance, fuzzy concept, presented by many authors as aggregation of economic, environmental and social performance of supply chain.
While sustainability information is typically treated separately, this paper tries to translate it into a form that corresponds to needs of decision-makers. This paper illustrates that it is possible to assess sustainable development in an integrated way that provides good guidance for decision-making. As the business case for sustainable practices becomes increasingly clear, sustainability reporting offers a measurable value to those whose business is to assess the current sustainability health of supply chains and influence future actions. At present, content of sustainability reports tends to appear in forms and units that are not readily convertible into unique terms. The module presented in this paper promises advance in sustainability assessment of supply chain and makes sustainability information more useful to decision-makers. Core and supplemental indicators (I Eco , I Env , I Soc ) when combined into global composite index (I g ) can be used to reflect the achievements of supply chain towards sustainability.
Even though further development is called for, it is evident that this module for sustainable development assessment has the potential to become very useful as one of the tools available. The combination of better assessment methods is likely to continue this movement towards a new generation of integrated sustainability performance reports.