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）