The sample of firms selected for this study relied on several benchmark dates: 1960, 1970, 1980, 1990, 2000, and 2005. The use of multiple benchmark dates avoids possible bias that could occur if only one of the dates had been selected. For example, if only 2005 had been considered, firms that were important in the 1960s or after but which had not remained in the ranking of the world's largest firms until the beginning of the twenty-first century would have been eliminated from this study, either because they had not survived or because they had not kept a pace of growth that allowed them to remain in the official rankings of the largest industrials such as Fortune 500. In the same way, if 1960 had been chosen as the only benchmark date, firms that had emerged as the largest at the end of the period of analysis would not have been included.

Several possible economic criteria could have been used in the selection of the firms to be included in this study. Value added, assets, market capitalization, and sales are just some examples of alternative measures. Although these measures might be equivalent in the long run, they offer valid but distinct perspectives on the performance of firms, each one with its own advantages and drawbacks.