The use of voluntary environmental protection instruments is expanding significantly around the world. Although there is a large literature dealing with what drives companies to adopt voluntary instruments, there has been relatively little research on the impact that some of these tools have on the actual environmental performance of companies. The existing literature in this area presents contrasting results, perhaps because it tends to use perceptual measurement, which may not reflect actual outcomes. To investigate this issue, the primary research reported on in this article undertook a combination of perceptual measurement and 'archival' (or objective) measurement on the same sample of firms. The research concluded that most firms saw some degree of positive response from the introduction of Environmental Management Systems. This was especially the case for 'system' (or 'process') improvements, and to a lesser extent held true for direct environmental performance improvements. It was also clear that there was a very close correlation between the results of the perception-based research and the archival measurement research. At least in the context of this kind of investigation, either research approach would appear to produce a valid outcome.
Keywords: archival measurement, environmental performance, perceptual measurement, perception, voluntarism, voluntary instruments, environmental protection, environmental management systems