We use a content analysis of the sustainability reports published by TNCs from Europe and North America from the mid-1990s to the present to address this question. We find that: (1) firms from both regions engaged earlier with environmental than social sustainability (2) firms continue to publish higher quality data on their environmental than their social impacts and (3) firms have adopted more ambitious improvement plans for their future environmental performance than for their future social performance. In the second part of the paper we seek to explain the observed differential engagement and argue that the ways in which norms of responsibility for social and environmental issues have become embedded in global markets at least partially account for this outcome. We support this view by contrasting how the business press and investor communities frame and promote environmental and social responsibility through their coverage of the issues and the accountability principles the latter have developed to define and measure them.