在本文中，我研究了價格效率是否降低公司進行盈餘管理的動機。我發現選擇權交易提供了有效的公司治理外部控制機制，確保經理人之決策符合股東最大利益的宗旨。實證結果闡述選擇權交易量較大的公司，其會計應計項目較低。 本文並使用 2010 年的政策衝擊進行DiD 測試，以排除可能的內生問題，結果也符合一致性。在橫斷面分析中，我發現分析師覆蓋率低和男性 CEO 的公司在選擇權交易對於減少盈利操縱的效果更為顯著。

In this paper, I investigate whether price efficiency reduces earnings manipulation. I find options trading provides an external mechanism that is intended to ensure the manager's behavior is consistent with the best interest of shareholders. I provide evidence that the firms with more options trading volume have lower total accruals. I use the 2010 policy shock to practice the difference-in-differences (DiD) test for ruling out the possible endogenous issues. Furthermore, I find the firms with low analyst coverage and with male CEO are more obvious in reducing the earning manipulation.

Table of contents
1. Introduction 5
2. Literature review 7
2.1 Option trading and information efficiency 7
2.2 Earning management and firm performance 8
2.3 option trading and earnings management 9
3. Methodology 10
3.1 Data 10
3.2 Variables 10
3.2.1 Options trading volume 10
3.2.2 Proxies for Earnings management 11
3.2.3 Control variables 11
3.3 Baseline Regression 12
4. Main Results 14
4.1 Panel regression 14
4.2 Difference-in-Differences Regressions 14
4.2.1 Parallel Trend Assumption 16
4.3 Mechanism 16
4.3.1 Analyst coverage and options trading 16
4.3.2 CEO gender and earnings management 17
5. Conclusion 19
6. References 20
7. Appendix 22

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