電子資訊業之高績效、大量研究發展支出及以股票為主的獎酬制度等產業特色，使得研究發展支出、內部人持股比率及公司績效間可能有相互的影響(內生關係存在)。本文以三階段最小平方方法(3SLS)，設立聯立方程式以比較內部人持股比率、研究發展支出及公司績效，在電子資訊業及非電子資訊業是否有不同的關聯性。 結果顯示電子資訊業在低內部人持股比率範圍時，內部人持股比率對公司績效有負向的影響，而內部人持股比率較高時，內部人持股比率對公司績效有正向的影響。此與非電子資訊業之結果相反。其可能原因為電子資訊業為了因應市場快速的變化，較集中的股權可能有利內部人之協商並於在短期內作重大的決議暨執行之。而在非電子資訊業，則發現內部人持股比率較低時，內部人持股比率對公司績效有正向的影響，符合利益收斂假說；而內部人持股比率較高時，內部人持股比率對公司績效有負向的影響，符合鞏固地位假說。此外我們發現一個有趣的現象，即基本上電子資訊業相對較非電子資訊業投入較多而穩定的研究發展費用以維持競爭力，但在非電子資訊業則公司績效愈高時，企業才會相對地提高研究發展支出。

The characteristics of high performance, high research expenditure and stock-based compensation plan of electric industry may relate insider stockholdings, research expenditure and firm performance as endogenous variables that are jointly determined. In this study, we apply three-stage least squares method (3SLS) to measure and compare the relevance of insider stockholdings, research expenditure and firm performance between electric and non-electric industries. Our results show that, in electric industry, within low insider stockholding range, increasing insider stockholdings has negative effect on firm performance; and within high insider stockholding range, higher stockholdings has positive effect on firm performance. The possible explanation is that higher insider ownership may help management to response to market quickly without spending lots of time in negotiation between insiders. While in non-electric industry, we find that within low insider stockholding range, insider stockholding has positive effect on firm performance, that agrees to convergence of interest hypothesis; but when insider hold over than average, firm performance will get worse, that agrees to entrenchment hypothesis. Furthermore, we find electric industry has higher and more stable research expenditure to maintain its competitive advantage than non-electric industry that spends more in research only when firm is doing well.