[[alternative]]存貨與裁決性應計數之估計

[[abstract]]本研究於Jones model (Jones 1991, Dechow et al. 1995) 及績效配對模型(Kothari et al. 2005)的基礎上，探討存貨具未來股票報酬之資訊內涵，是否影響裁決性應計數的估計模式。Chan et al. (2006)及Thomas and Zhang (2002)皆發現應計數與未來股價報酬呈負相關的原因(Sloan, 1996)，主要來自存貨項目，代表存貨具有不同於其他應計項目之資訊內涵。藉由放寬Dechow et al. (1998)的模型假設，察覺存貨變動除了與當期銷貨變動相關外，也受銷貨收入函數的隨機過程及經理人存貨決策的影響。而經理人的決策依過去存貨與銷貨的資訊及對未來的銷貨預期而定，故不能僅以當期銷貨變動估計正常的存貨變動。因為存貨反映過去、現在及未來資訊，本研究依此估計一個包括過去、現在及未來資訊的正常存貨變動數(NorΔInv)，加入Jones model中，改善僅以當期銷貨變動估計非裁決性應計數的不足處。研究的模擬結果指出，正常存貨變動數(NorΔInv)可減少裁決性應計數的估計誤差，提升盈餘管理研究結果的可信度。 This study examines the role of inventory on estimates of discretionary accruals. Chan et al. (2006) and Thomas and Zhang (2002) indicate that the negative relation between accruals and future abnormal returns pointed out by Sloan (1996) is due mainly to changes in inventory, so there is more information in changes in inventory than in other accrual items. This paper modifies the model of Dechow et al. (1998) to show that changes in inventory do not just depend on changes in sales, but both on generation processes of sales and managers＇ inventory policies. As mentioned above, it is not appropriate to only using current changes in sales to estimate normal changes in inventory, one of nondiscretionary accrual items. However, few studies have been done on the effect of inventory on estimation of discretionary accruals. To overcome this shortcoming, a control variable, normal change in inventory (NorΔInv), that captures the past, current, and future information in inventory is present in this paper. After adding the control variable, NorΔInv, to Jones, modified-Jones and performance-matched models, this study examines the specification and the power of tests based on the discretionary accrual measures with NorΔInv and compares with tests using original discretionary accrual measures. The results suggest that adding NorΔInv to Jones, modified-Jones and performance-matched models can enhance the reliability of inferences from earnings management research