The sentence “The global average of corporate boards’ gender diversity for all the sectors during 2008-2018 was about 13.5%” is correct as it is calculated based on all industries (5120 firms in total). However, since we are focusing on “Mining, Quarrying, and Oil and Gas Extraction Industry”, it makes more sense indeed to report the value for that particular sector. Therefore, we update the text as follows: “The average of corporate boards’ gender diversity for Mining, Quarrying, and Oil and Gas Extraction Industry during 2008-2018 was about 9.6%”.
Overall, I believe that this study has a high potential to add to the literature on the relationship between gender diversity and firm environmental performance.