Summary
Voluntary sustainability standards (VSS) have proliferated over the last two decades. Currently there are at least more than 400 schemes operating internationally. The paper starts with a description of the emergence, proliferation and global diffusion of VSS. It subsequently focuses on the diversity between systems in the wider group of VSS. What emerges is a diverse and growing (both on the supply and demand side) market of VSS. This proliferation and diversification of VSS is creating problems such as a credibility gap, increased costs to gain certification by multiple VSS systems and a potential race to the bottom of systems. These problems point to the need for increased cooperation between VSS systems. Next, the paper introduces and discusses two mechanisms which can facilitate more cooperation, mutual recognition and meta]regulation. Mutual recognition is especially suited to address cost issues, while meta-regulation might contribute to leveling the playing field. The paper analyzes these mechanisms and argues that cooperation in the market of VSS is currently more developed with regard to addressing the credibility gap (meta-regulation) rather than with regard to addressing the cost issue (mutual recognition).