本研究探討分析師追蹤公司家數與其盈餘預測準確度之關聯，考量分析師之時間與認知資源有限，當分析師同時追蹤較多公司時，可投入於單一公司之研究時間與資訊處理資源相對減少，進而降低盈餘預測準確度。本研究以分析師追蹤公司家數為出發點，引入產業集中度作為調節變數，檢視產業集中度是否能調節前述負向關係，並以短期及長期累積異常報酬作為市場反應之衡量指標，進一步檢驗市場是否能識別不同分析師因追蹤公司家數與產業結構差異所形成之資訊優勢。研究期間為2014年至2024年之美國企業資料。實證結果顯示，分析師追蹤公司家數越多，其盈餘預測準確度顯著越差，支持認知資源有限之觀點；惟產業集中度未能對上述關係產生預期之正向調節效果。此外，以短期及長期累積異常報酬衡量市場反應時，分析師追蹤公司家數與產業集中度之交互效果未達統計顯著，顯示市場未能有效反映不同分析師因追蹤公司家數與產業結構差異所形成之資訊優勢。;This study examines the relationship between the number of firms followed by analysts and their earnings forecast accuracy. Considering that analysts have limited time and cognitive resources， when analysts follow more firms simultaneously， the research time and attention allocated to each individual firm may decrease. Based on limited attention theory， this study expects that following more firms will reduce analysts’ earnings forecast accuracy. This study uses the number of firms followed by analysts as the key explanatory variable and introduces industry concentration as a moderating variable to examine whether industry concentration moderates the negative relationship between analysts’ coverage scope and earnings forecast accuracy. In addition， short-term and long-term cumulative abnormal returns are used as measures of market reaction to further examine whether the market can identify the information advantage arising from differences in analysts’ coverage scope and industry structure.Using U.S. firm data from 2014 to 2024， the empirical results show that analysts who follow more firms have significantly lower earnings forecast accuracy， consistent with the prediction of limited attention theory. However， industry concentration does not provide the expected positive moderating effect on this relationship. Furthermore， when market reaction is measured by short-term and long-term cumulative abnormal returns， the interaction effect between the number of firms followed by analysts and industry concentration is not significantly reflected in market reactions.
