This part of the book is transitional in nature, for we conclude some of the strands in the arguments presented in previous parts, and we broaden the scope of our inquiry into other directions. One issue that stands out above all others in this context is the validation of the theory. The theoretical analysis of Part I identified clearly the main causes or determinants of shift-work at the level of the firm, but the discussion of estimation and the review of the empirical literature in Part II revealed the difficulty of undertaking appropriate empirical tests that will corroborate or deny the existence of these causal relationships. The individual-country results presented in this chapter bring together these two aspects of the issue by providing evidence on the validity of the theory after correcting for the econometric problems that cloud the interpretation of previous results. In Chapter 8 we move on to other dimensions of the topic. There we present evidence on the extent to which the theory previously developed explains differences in shift-work among the countries in our UNIDO data, and we summarize the available evidence on the extent and the main characteristics of shift-work in various countries. This summary provides some motivation for the subsequent discussion in Part IV, which focuses on the effects of shift-work at the economy-wide level as well as at the firm level.