The article Effects of Supplier and Customer Integration on Product Innovation and Performance in the Journal of Product Innovation Management has some empirical evidence on impact of co-design and information sharing with suppliers and customers:
After surveying 251 manufacturers in Hong Kong, this study tested the relationships among information sharing, product codevelopment, product innovativeness, and performance with three control variables (i.e., company size, type of industry, and market certainty).
The findings seem to indicate a direct, positive relationship between supplier and customer integration and product performance. However, there are a couple of key learnings: For brand new product families (that have not yet percolated through the supply-chain), it is much more important to partner with the emerging customer to learn and perfect the product. On the other hand, for improving existing product lines, it pays to work with suppliers. Information sharing with existing customers is not that important, but customer intimacy is:
The empirical findings show that product codevelopment with suppliers improves performance, mediated by innovation. However, the sampled firms cannot improve their product innovation by sharing information with their current customers and suppliers as well as codeveloping new products with the customers. If the adoption of supplier and customer integration is not cost free, the findings of this study may suggest firms work on particular supplier and customer integration processes (i.e., product codevelopment with suppliers) to improve their product innovation. The study also suggests that companies codevelop new products only with new customers and lead users instead of current ones for product innovation.