本研究以2007年至2023年之美國上市公司為樣本，旨在探討執行長任期、執行長語調與企業多角化程度之關聯，並檢驗語調於任期與多角化決策間之中介效果。實證結果顯示，執行長任期與語調呈倒U型關係；前期隨權力與信心累積使語調趨於正向，後期則因職涯擔憂緩解且轉向守成，使語調正向程度下降。執行長任期與多角化程度則呈顯著負相關，顯示前期風險承擔意願與擴張動機較高，後期則固守於既定思維並維護經營成果，進而減少多角化投資。此外，語調對多角化策略之影響亦呈顯著負相關，反映語調下降隱含執行長對營運之擔憂，進而透過多角化分散經營及個人職涯風險。
再者，中介效果之檢驗說明任期對多角化決策之影響部分係透過語調傳遞，顯示語調反映執行長隨職涯階段改變之風險判斷。額外分析則指出，多角化存在企業價值減損的現象，且於執行長解任風險較低之任期後期更為顯著。最後，以異常語調進行穩健性測試後仍與主結果一致，證實執行長語調對企業策略具備獨立於財務績效外之解釋力。

Using a sample of U.S. public companies from 2007 to 2023, this study investigates the relationships among CEO tenure, CEO tone, and firm diversification, and examines the mediating effect of tone between tenure and diversification decisions. Empirical results indicate an inverted U-shaped relationship between CEO tenure and disclosure tone. In the early stage of tenure, CEO tone becomes more positive as expert power and managerial confidence accumulate; in the later stage, the positivity of tone declines due to the mitigation of career concerns and a shift toward conservatism. Furthermore, CEO tenure is significantly and negatively correlated with the degree of diversification, suggesting that early-tenure CEOs possess higher risk-taking willingness and expansion motives, while late-tenure CEOs tend to adhere to established mindsets and preserve operational outcomes, thereby reducing diversification investments. In addition, the direct effect of tone on diversification is significantly negative, reflecting that a less positive tone implies the CEO’s concerns regarding firm operations, which prompts them to pursue diversification to hedge against operational and personal career risks.
Moreover, the mediation analysis demonstrates that the impact of tenure on diversification is partially transmitted through tone, indicating that disclosure tone reflects a CEO’s evolving risk judgments across career stages. Additional analysis reveals that diversification results in a decrease in firm value, which is more pronounced in the later stages of tenure when CEOs face lower dismissal risk. Finally, robustness tests using abnormal tone remain consistent with the primary findings, confirming that managerial disclosure tone holds independent explanatory power for corporate strategy beyond objective financial performance.

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