This dissertation has three chapters studying accounting conservatism in the property-liability (P&L) insurance industry. There are two types of accounting conservatism - ex-ante (unconditional) conservatism and ex-post (conditional) conservatism. The former means that firms over-report liabilities initially, before more detailed information becomes available. The latter means that firms respond to this new information asymmetrically by recognizing expected losses more quickly than expected gains. My analysis throughout the dissertation focuses on the loss reserve accruals since it is the most significant accruals on the balance sheet. One benefit of studying the P&L insurance industry is that we have specific and detailed information regarding the development of loss reserve accruals over time. Chapter 1 is an executive summary of the next two chapters, highlighting the key results, the policy implications, and the contributions of the dissertation. Chapter 2 studies the two types of accounting conservatism and explore three research questions: (1) whether ex-ante and ex-post conservatism prevails in the P&L insurance industry; (2) what the relations are between ex-post conservatism and other managerial incentives including ex-ante conservatism; and (3) how much the opportunity cost is for being conservative. I study all U.S. domiciled P&L insurance companies from 1996 to 2012 and follow the previous literature to measure accounting conservatism in Chapter 2. I find that both types of accounting conservatism prevail in the insurance industry. Besides, the back-of-the-envelope estimates based on the industry average insurer indicate that their opportunity costs are trivial compared to the amounts of net income and total assets. Chapter 2 also shows that the practices of ex-ante and ex-post conservatism exhibit a nonlinear, U-shape relationship. This finding supports the view that the two types of conservatism can be compliments because they can serve for different purposes. Ex-ante conservatism is mainly used to create a cushion against future unexpected losses, whereas ex-post conservatism can reduce informational frictions. In Chapter 3, I develop a new method of assessing conditional conservatism using more detailed data from the insurance industry. I look at how conditional conservatism affects insolvency risk and the financial strength rating of P&L insurance companies. I also investigate how a change to accounting rules affects conditional conservatism. The new method of measuring conditional conservatism is based on the concavity of the loss development curve. I study all U.S. domiciled P&L insurance companies from 1995 to 2015 and find that the greater the degree of conditional conservatism, the lower is insolvency probability, and the better is the financial strength rating, with other things being constant. The result indicates that regulators and rating agencies do reward insurers that voluntarily utilize conditional conservatism accounting strategy. Moreover, I find that the level of conditional conservatism is reduced after the enactment of the Model Audit Rule (MAR). MAR, like the Sarbanes-Oxley Act Section 404, increased board oversight of internal risk management. The result suggests that complying with additional disclosure requirements provides a "safe harbor" for insurance companies so that they have fewer incentives to be conditionally conservative.