ایزو 9000 و کارایی زنجیره تامین:شواهد تجربی در مورد موجودی و روزهای حسابهای دریافتی

ISO 9000 is the most popular and widely adopted meta-standard for quality and operational improvements in manufacturing supply chains. However, few studies have quantitatively examined its impact on supply chain efficiency. In this paper we measure the material and cash flow efficiency of ISO 9000 certified firms in terms of inventory days and account receivable days. We analyzed changes in these time-based efficiency indicators prior and after ISO 9000 implementation in 695 US-listed manufacturing firms. We found that ISO 9000 certified firms shortened the number of inventory days by 3.68 days 1 year after ISO 9000 implementation. They showed continuous improvement and shortened the number of inventory days by 8.75 days (8.29% shorter) 3 years after certification. Account receivable days and overall operating cycle time also showed similar significant reductions after ISO 9000 implementation. The results reveal that ISO 9000 adoption helps improve the material and cash flows in manufacturing supply chains.

Due to globalization of the world economy, organizations are looking for international standards that foster easier trade and reduce trade barriers linked to national standards (Boiral, 2003). ISO 9000, a meta-standard for quality management (QM), has become such an international standard that serves as a key selection criterion for supplier selection (Curkovic and Handfield, 1996; Goffin et al., 1997). Since its introduction, ISO 9000 has become the passport to global business (Uzumeri, 1997) and a basic requirement for government tenders in many countries. It diffuses along the supply chain due to customer pressure or government policies (Corbett, 2003; Corbett and Kirsch, 2001; Guler et al., 2002). Most practitioners believe that ISO 9000 certified companies provide timely responses and high quality supplies, rendering them more competitive in their supply chains. Moreover, previous research has found that there is a direct relationship between QM practices and supply chain performance (Flynn and Flynn, 2005). Although much research has been conducted on the organizational impacts of ISO 9000, most of them were survey-based studies with subjective data, producing few conclusive results. Some previous empirical works suggested that ISO certification has little benefit for operational efficiency (Corbett and Kirsch, 2001; Terziovski et al., 1997) and mixed impacts on financial performance (Corbett et al., 2005; Terziovski et al., 2003; McGuire and Dilts, 2008). These findings are at odds with the global phenomenon of rapid diffusion of business certifications. The number of ISO 9000 certified companies has been rising over time, sustaining an annual growth rate of about 20%. Other industry specific QM standards, such as QS 9000, TL 9000 and ISO 13485, have been developed to meet growing demands for meta-standards in the automobile, telecommunications and medical devices industry sectors. Suppliers of raw materials and components in these sectors need to pursue the corresponding certifications to attain competitive advantages. Through standardization and systemization as a result of ISO 9000 adoption, the operational procedures of the adopting company should be more efficient. Many companies perceive that implementing ISO 9000 can improve operational performance. Despite the perceived benefits of operational efficiency improvement, a number of critics argue that the extra documentation efforts required by ISO registration are time-consuming, and ISO adoption provides no real benefits to business performance (Aarts and Vos, 2001; Heras et al., 2002; Terziovski et al., 1997). The aim of this study is to provide empirical evidence on the impact of ISO 9000 on the material and cash flows of certified companies with a view to knowing whether ISO 9000 certified firms become more efficient nodes in their supply chains. We carried out an event study analysis and compared ISO 9000 certified with non-ISO 9000 certified firms by controlling industry type, firm size and pre-certification performance. We compared changes in inventory days, account receivable days, and overall operating cycle time of each sample firm with those of a portfolio of control firms that fitted our matching criteria.

We found that publicly listed manufacturing firms in North America implementing ISO 9000 significantly improved the time-based efficiency of their operations. The time-based efficiency started to improve right after ISO 9000 implementation. We found that ISO 9000 certified firms continued to perform better in terms of attaining a shorter operating cycle three years after they obtained certification. We believe that these operational improvements have important implications for supply chain efficiency as they mean faster cash and material flows between suppliers and customers. The abnormal performance of shortened account receivable days also suggests that ISO 9000 certified firms could offer better customer service and higher product quality. Therefore, the diffusion of ISO 9000 along the global supply chain (Corbett, 2003) will create an enormous impact on total supply chain efficiency in the long run. Some supply chains have their own quality certification requirements to ensure that suppliers in the supply chain follow the same quality management structures. For example, ISO 19649 (formerly QS-9000) of the automobile supply chain was developed to address the specific needs of the automobile industry, such as component reliability and safety (Arunachalam et al., 2002; Lin et al., 2004). The results of this study indicate that these efforts are likely to pay off in terms of faster material and cash flows among supply chain members. Operating cycle time is a commonly used performance measure in scheduling research. However, it has rarely been investigated in empirical studies in operations management. In fact, with clear implications for operational efficiency, operating cycle time and its components are sound time-based efficiency indicators for research in supply chain management. Quality and operations management researchers should consider including such time-based efficiency indicators in future research. As for the limitations of this study, although we controlled industry type by 2-digit SIC codes, more accurate results would be obtained if we could match three or even four digits of the codes. According to previous research based on the event study methodology (e.g., Corbett et al., 2005; Hendricks and Singhal, 1997; Naveh and Marcus, 2005), 2-digit SIC codes provide a good balance between control on industrial type and availability of control firms. To control firm size (total assets), we adopted a 33–300% range in matching control firms, which might also be considered to be quite wide. Nevertheless, in this study we adopted a tighter control on pre-certification performance, which was empirically shown to be the most significant control factor in event studies (Barber and Lyon, 1996). The ISO 9000 series has a standard set of technical contents and requirements, which are adopted by both services and manufacturing firms across nations. However, research has shown that manufacturing firms in different countries are under different levels of institutional pressure to adopt ISO 9000 (Guler et al., 2002). In fact, manufacturing firms in North America may face relatively less institutional pressure compared with their counterparts in Europe or China. For example, Chinese manufacturing firms, which are mainly OEMs and predominantly export-oriented, are under high institutional pressure to adopt various QM standards (Yeung et al., 2003). As a result, ISO 9000 certified firms in China may only pursue the symbolic value of certification and adopt the standard with an unenlightened motivation. In this case, real improvement in time-based efficiency in adopting firms residing outside North America would be questionable. Replication of our study for manufacturing firms in China or other non-North American countries would be important for future research. In conclusion, we found that ISO 9000 certified firms’ time-based efficiency improved significantly after certification compared with non-ISO 9000 certified firms. In the long-run, the length of the operating cycle gradually decreased in ISO 9000 certified firms. This finding provides empirical evidence that ISO 9000 is associated with supply chain efficiency.