近年來，多角化與公司績效的關係一直是學者關心的議題。過去大部分文獻針對保險產業討論為少，更較少考慮再保險對多角化與績效之關係的調節效果。

從過去的文獻，我們發現再保險對於保險公司績效有其影響。本研究同時考量多角化與再保險的觀點，檢視再保險與多角化交互作用對於產險公司績效的影響。我們更使用清償能力作為公司績效的管理衡量。我們使用1986到2006年S&P SynThesys Non-Life資料庫，以英國產險公司為研究樣本，並使用迴歸分析的方式來檢驗多角化與績效及多角化與再保險之交互作用與公司績效的關係。

我們發現結果與過去討論保險產業之文獻相符，產品多角化會降低公司績效，產生所謂的「多角化折價(diversification discount)」的效果。而我們也發現地理多角化與公司績效呈現S型關係，再保險的調節效果則顯著地呈現負向關係。最後，我們的結果也指出集團效果對公司績效並不一定為正向效應，但對於公司清償能力則會有所提升。股份保險公司相較相互保險公司之績效為佳。

In recent decades, insurers have been increasing their lines of business and interantional domains. Under these two strategies, scholars have disputed the imapct of diversification under the discussion of benefits and costs that it may cause. Previous literature has provided different evidence on the effect of product and geographic diversification on insurer performance. Our study intends to survey the recent developments in the impact of diversification based on the data for the United Kingdom insurers in the period of year 1986 to 2006. Besides, we extend the stream of research by investigating the existence of moderating role of reinsurance on the relationship between diversification and performance.

We find that product diversification consistently has a negative impact on risk-adjusted return on asset and equity and insurer solvency. In addition, we suggest a sigmoid relationship between geographic diversification and firm performance. As for moderating effect, however, the use of reinsurance do not benefit internationally diversified insurers. We also find affiliated insurers do not necessarily have higher returns but may have lower insolvency risk. Stock insurers are significantly profitable than mutual insurers.

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