We identified four instrumental variables at the time of investment that met the necessary criteria identified by Bascle (2008): 1) industry sales growth; (行业销售增长)
2) the eight-firm concentration ratio (both calculated at the two-digit SIC code level); (CR8,按照SIC-2细则分类)
3) the number of trade associations the VC is a member of; (VC所属行业协会数量)
4) the number of states in which a VC's portfolio firms that have gone public are located in minus 1 (to remove the focal firm's state(风投投资组合公司上市所在州的数量为减1,这里的focal firm不知如何理解)
括号里是我理解的翻译(请大佬帮忙修改与翻译)