The Effect of Proposition 103 on Insurers: Evidence from the Capital Market Introduction On November 8, 1988, California voters passed an insurance-reform ballot initiative known as Proposition 103. In essence, the initiative was a populist response to rising automobile insurance premiums in a state where property-liability insurance rates were already among the highest in the nation. Proposition 103's most controversial provision mandates a minimum 20 percent reduction in property-liability insurance premiums from their November 1987 levels. An exemption from the rate cut and any future rate increases were to be permitted only if an insurer was substantially threatened by insolvency. On May 4, 1989, the California Supreme Court upheld the constitutionality of the rate rollback but overturned the insolvency provision and ruled that insurers were entitled to an adequate return. Comments in the financial press indicate that Proposition 103 has evoked a considerable debate about its effect on the property-liability insurance industry. Opponents of Proposition 103 have deemed it to be one of the most expensive political defeats any American industry has faced. This view is based on several features of Proposition 103 (see Gross, 1989; and Schmitt and Steptoe, 1988). First, the 20 percent rollback in premiums is estimated to produce an annual loss of $6 billion for the insurance industry. Second, revenues earned by the property-liability industry are further reduced because Proposition 103 introduces more competition into the insurance market by allowing Califoria banks to act as insurance brokers or agents. Third, because of the proposition, the insurance industry is no longer exempt from the state's antitrust laws. This would effectively curtail the widespread practice of exchanging and pooling actuarial and other data. Insurers contend that exchanging information is useful in setting accurate and fair rates. Moreover, they argue that removal of the exemption threatens the soundness of medium-size companies which depend on pooled actuarial data to make sound estimates of risk. An alternative view expressed by some groups is that the regulatory changes instituted by Proposition 103 may ultimately benefit the insurance industry. For example, some industry experts argue that by injecting the adequate return standard into Proposition 103, the decision rendered by the state high court is favorable to insurers in California. As most California auto insurers claim to be earning little or no return in the state (see Hill and Celis, 1989), the adequate return standard provides a loophole that may largely negate the 20 percent rate reduction provision. Moreover, some observers believe that under Proposition 103 insurance rates will increase rather than fall if insurers can demonstrate that their current rate structure deprives them of an adequate return. (1) According to Standard and Poor's, the adequate return clause was a positive development for insurance firms operating in California. Indeed, as a result of the court decision, the rating agency removed two large California insurers, Safeco and Allstate, from its credit-watch list (see Schmitt and Wells, 1989). While the debate on the effects of Proposition 103 on the insurance industry continues, no empirical evidence has been presented on how the California initiative affected the shareholders of property-liability insurers. This study examines share price reactions of property-liability insurers around key dates surrounding Proposition 103. The findings indicate that Proposition 103 is viewed by the capital market as an unfavorable development for insurers. Data and Research Methods A preliminary sample of firms most likely to be affected by the consequences of Proposition 103 is identified from the list of "The Two Hundred Largest American Property-Casualty Companies" published in Best's Key Rating Guide (1988) (2) and from articles discussing the California initiative in the Wall Street Journal (WSJ). …