Selecting the right methodology to study corporate environmental performance and practice is not an easy task

The survey methodology is weakened by relatively low response rates (which makes the sample less representative), by the inability of researchers to probe general responses for concrete details and other supportive evidence, and by the noncomparability of the respondents’ different industrial and ecological contexts. The in-depth case studies of one or a few firms are more reliable, but are weaker in explanatory power and external validity. The large majority are also highly selective, being ‘‘success stories’’ that provide insights but from which it would be very dangerous to generalize. Moreover, they are not capable of explaining variation between firms--our key research challenge.  (p. 53)

Verbatim from:

Kagan, R. A., N. Gunningham, et al. (2003). "Explaining corporate environmental performance: How does regulation matter?" Law and Society Review 37(1): 51-90+1.