Effects of Corporate Diversification: Evidence From the Property–Liability Insurance Industry
基于1995-2004年美国财产责任保险公司数据，研究发现业务多元化的保险公司在会计和市场绩效上均显著低于专业化公司，存在多元化惩罚和折价，支持战略聚焦假说。
Abstract Using a sample of property–liability insurers over the period 1995–2004, we develop and test a model that explains performance as a function of line‐of‐business diversification and other correlates. Our results indicate that undiversified insurers consistently outperform diversified insurers. In terms of accounting performance, we find a diversification penalty of at least 1 percent of return on assets or 2 percent of return on equity. These findings are robust to corrections for potential endogeneity bias, alternative risk measures, alternative diversification measures, and an alternative estimation technique. Using a market‐based performance measure (Tobin's Q) we find that the market applies a significant discount to diversified insurers. The existence of a diversification penalty (and diversification discount) provides strong support for the strategic focus hypothesis. We also find that insurance groups underperform unaffiliated insurers and that stock insurers outperform mutuals.