*3.3. Independent Variables*

It is necessary for independent variables to have the capacity to measure the values referred to by the framework predictions. Hypothesis 1 refers to board independence. In studies on Italian listed companies and studies conducted on other stock markets, board independence is measured as the proportion of independent directors on the board [2,70]. Therefore, for the conclusion of every observed year, the number of independent members on each firm's board divided by the sum of people on the board was measured as the variable board independence. The profile of the board members at our sampled firms was evaluated by referring to the companies' internet sites and their 'Relazione sulla corporate governance' (Report on Corporate Governance: something every listed company renders public on its internet site). Hypotheses 2 and 3 refer to the use of ERP digital technology. For this aim, we used the variable proxy ERP spending, which we measured as the expenditure for the use of ERP technologies for every one of our sampled firms at the conclusion of each observed year divided by total assets. This variable was measured as a percentage. Data on expenditures made were obtained by asking each firm in the sample to complete a brief questionnaire regarding their expenditure on the acquisition and implementation of ERP technologies over the years.

#### *3.4. Control Variables*

In order to check for a range of factors that might have an impact on a firm's environmental performance, a series of variables at the firm level were looked at. In particular, by using the AIDA databases (Bureau van Dijk) and Datastream databases (Thomson Financial), we obtained the financial and market data we needed to be able to control for:

