過去對公司分割的研究焦點主要集中在母公司的宣告效果，並且這些研究一致發現市場對於公司宣告分割的效果都是正面。我們預期既然過去研究的結果是如此的一致且顯著，那麼母公司宣告分割的效果應該對於其上下游廠商也會造成某種程度的影響。
過去有很多研究提出不同理論來解釋為何當公司宣告分割時，會有正的財富效果。因此、我們根據過去研究所提出的理論來建構本研究的假設，並採用Sahrur(2005)的研究方法找出母公司的主要上下游廠商，最後檢定當母公司宣告公司分割時對他們的上下游廠商所產生的財富效果。
實證的結果顯示當公司宣告分割時，其上下游廠商產生的財富效果會與效率提升假說和資訊不對稱改善假說的預期一致，但是卻與財富移轉假說的預期方向相反。因此、我們推論公司宣告公司分割時，母公司的上下游廠商可能會同時受到效率提升假說與資訊不對稱改善假說的影響。

Previous studies mainly focus on the wealth effects of spin-offs on the parent firms and all these studies consistently find that stock markets give positive reaction to spin-off announcements. We expect if spin-offs can bring very consistent and significant effects on the parents firms, spin-offs might have certain influence which could be extended to the parents’ suppliers and corporate customers.
There have been several theories provided to explain why spin-offs can create values to the parent firms. Thus, we base on these theories and develop our hypotheses. Then, we follow Shahrur’s (2005) method to identify the parents’ key suppliers and customers and then empirically examine the wealth effects on the suppliers and customers.
Our empirical results suggest that both parents’ suppliers and customers have positive wealth effects when spin-offs are announced. This finding indicates that efficiency improvement hypothesis and mitigation of information asymmetry hypothesis may exist simultaneously and are more dominant than wealth transfer hypothesis.

References
Aboody, David; Lev, Baruch. (2000), "Information asymmetry, R&D, and insider gains" Journal of Finance, 55 (6), 2747-2766.
Ahn, Seoungpil; Denis, David J. (2004), "Internal capital markets and investment policy: evidence from corporate spinoffs," Journal of Financial Economics, 71 (3), 489-516.
Allen, R. F. (1983), "Efficiency, Market Power, and Profitability in American Manufacturing," Southern Economic Journal, 49 (4), 933-40.
Alli, K., G. G. Ramirez, and K. K. Yung (2001), "Withdrawn spin-offs: An empirical analysis," Journal of Financial Research, 24 (4), 603-16.
Best Ronald W., Roger J. Best, A. M. Agapos (1998), "Earnings Forecasts and the Information Contained in Spinoff Announcements," Financial Review, 33 (3), 53-68.
Burch, Timothy R.; Nanda, Vikram (2003), "Divisional diversity and the conglomerate discount: evidence from spinoffs," Journal of Financial Economics, 70 (1), 69-98.
Chemmanur, T. J. and I. Paeglis (2001), "Why issue tracking stock? Insights from a comparison with spin-offs and carve-outs," Journal of Applied Corporate Finance, 14 (2), 102-14.
Chemmanur, T. J. and A. Yan (2004), "A Theory of Corporate Spin-offs," Journal of Financial Economics, 72 (2), 259-90.
Comment, R. and G. A. Jarrell (1995), "Corporate focus and stock returns, Journal of Financial Economics," Vol, 37 (1995), 67-87.
Cusatis, P. J., J. A. Miles, and J. R. Woolridge (1993), "Restructuring through spinoffs: The stock market evidence," Journal of Financial Economics, 33 (3), 293-311.
Dahlstrand, A. L. (1997), "Growth and inventiveness in technology-based spin-off firms," Research Policy, 26 (3), 331-44.
Darrough, M.; Rangan, S. (2005), "Do insider manipulate earnings when they sell their shares in an intial public offering?," Journal of Accounting Research, forthcoming.
Daley, Lane; Mehrotra, Vikas; Sivakumar, Ranjini (1997), "Corporate focus and value creation Evidence from spinoffs," Journal of Financial Economics, 45 (2), 257-81.
Desai, Hemang; Jain, Prem C. (1999), "Firm performance and focus: long-run stock market performance following spinoffs " Journal of Financial Economics, 54 (1), 75-101
Dittmar, Amy (2004), "Capital Structure in Corporate Spin-Offs," The Journal of Business, 77 (1), 9-35.
Fan, J. P. H. and L. H. P. Lang (2000), "The Measurement of Relatedness: An Application to Corporate Diversification," The Journal of Business, 73 (4), 629-60.
Fee, C. E. and S. Thomas (2004), "Sources of gains in horizontal mergers: evidence from customer, supplier, andrival firms$," Journal of Financial Economics, 74, 423-60.
Frankel, Richard M. and Xu Li (2004), " Characteristics of a Firm's Information Environment and the Information Asymmetry Between Insiders and Outsiders," Journal of Accounting and Economics, 37(2), 229-59.
Gertner Robert, Eric Powers & David Scharfstein (2002), "Learning about Internal Capital Markets from Corporate Spin-offs," The Journal of Finance, 57 (6), 2479-506.
Hertzel, M. G., M. S. Officer, and K. J. Rodgers (2004), "Inter-firm Linkages and the Wealth Effects of Financial Distress along the Supply Chain: Rivals, Customers, and Suppliers," Working Paper.
Hite Gailen L., James E. Owers (1983), "Security price reactions around corporate spin-off," Journal of Financial Economics, 12 (4), 409-36.
John, K. and E. Ofek (1995), "Asset sales and increase in focus," Journal of Financial Economics, 37 (1), 105-26.
John, T. A. (1993), "Optimality of Spin-Offs and Allocation of Debt," The Journal of Financial and Quantitative Analysis, 28 (1), 139-60.
Johnson, S. A., D. P. Klein, and V. L. Thibodeaux (1996), "The Effects of Spin-offs on Corporate Investment and Performance," Journal of Financial Research, 19 (2), 293-307.
Krishnaswami, S., Subramaniam, V. (1999), "Information asymmetry, valuation, and the corporate spin-off decision," Journal of Financial Ecnomics, 53, 73-112.
Lang, Larry H. P., Stulz Rene M.. (1992), "Contagion and competitive intra-industry effects of bankruptcy announcements," Journal of Financial Ecnomics, 32, 45-60.
Lin, Ping (2006), "Strategic Spin-offs of Input Divisions," European Economic Review, 50, 977-93.

Maxwell, W. F., Rao, R. P. (2003), "Do Spin-offs Expropriate Wealth form Bondholders?," The Journal of Finance, 58 (5), 2087-108.
Mehrotra, V., Mikkelson, W., Partch, M. (2003), "The Design of Financial Policies in Corporate Spin-offs," Review of Financial Studies, 16 (4), 1359-88.
Nanda, V. and M. P. Narayanan (1999), "Disentangling Value: Financing Needs, Firm Scope, and Divestitures," Journal of Financial Intermediation, 8 (3), 174-204.
Opler, Tim C., Titman, Sheridan (1994), "The Financial Distress and Corporate Performance," The Journal of Finance, 49 (3), 1015-1040.
Parrino, Robert (1997), "Spinoffs and wealth transfers: The Marriott case," Journal of Financial Economics, 43 (2), 241-74.
Schipper Katherine, Abbie Smith (1983), "Effects of recontracting on shareholder wealth :The case of voluntary spin-offs," Journal of Financial Economics, 12 (2), 437-67.
Shahrur, H. (2005), "Industry structure and horizontal takeovers: Analysis of wealth effects on rivals, suppliers, and corporate customers," Journal of Financial Economics, 76 (1), 61-98.
Slovin, M. B., M. E. Sushka, and S. R. Ferraro (1995), "A comparison of the information conveyed by equity carve-outs, spin-offs, and asset sell-offs," Journal of Financial Economics, 37 (1), 89-104.