ISO 9000 and supply chain efficiency: Empirical evidence on inventory and account receivable days

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.