This paper was published as a Faculty Working Paper (no. 210) for the Lubin School of Business, Center for Applied Research, August 2003.

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Most of the accounting research examining the information content of earnings assumes a competitive market framework. Little research has been devoted to the value relevance of earnings announcements in regulated markets. This paper examines the information content of earnings releases under two economic conditions facing the airline industry: regulation and deregulation (i.e., competition). We hypothesize that in a deregulated (competitive) environment, there is greater competition, causing more risk and uncertainty for the investor in setting security prices. Therefore, earnings' releases provide more useful information in resolving uncertainties and in formulating and revising the investor's beliefs regarding future earnings and prices in deregulated than for regulated markets.

Three critical event periods are examined: the regulation period (1973 - 1975), the transition period (1976 - 1978), and the deregulation period (1979 - 1981). A revaluation index (RI) and a standardized revaluation index (SRI) are used to examine the extent of airline stock price revaluation in response to quarterly accounting earnings releases during the three critical event periods. The results indicate that earnings announcements have value relevance in setting security prices in both regulated and deregulated market conditions. However, the level of the market revaluation to earnings releases is dependent on market structure. The market revaluation to earnings releases is greater in a deregulated (competitive) period than in a regulated one. This result confirms the hypothesis that earnings have more value relevance in competitive markets than in regulated ones. The findings of this research have direct implications for the level of accounting disclosure and the extent of financial reporting in a given market structure. Since financial reporting is a costly process, it becomes important to identify the circumstances under which the level of financial disclosure should be expanded or reduced