美國在兩岸關係中的第三方影響：一個時間序列的分析途徑

The Role of the United States in Cross-Strait Relations: A Time Series Analysis Approach

兩岸關係是否應置於美中臺三角關係脈絡中分析？本文將運用時間序列分析，並利用1979年以來的事件資料庫，檢證美中臺三方互動是否影響兩岸互動行為，並回答以下兩個問題。第一，事件資料庫的統計檢驗，是否支持美國行為在兩岸互動中扮演顯著角色？第二、若是，則自1979年以來，美國如何影響兩岸關係？本文的分析結果顯示，美中臺三角互動與兩岸行為模式，兩者間具有因果關係。美國行為的確能夠影響兩岸互動，但是其影響相當有限且間接。首先，美國對臺行為，將改變中國對臺行為的衝突或合作程度；再者，臺灣對美政策是影響臺灣對中政策行為穩定性的重要因素。另外，兩岸間的雙邊影響也是兩岸發展的重要因素，但是本文更加精確地說明以下兩個事實。第一，臺灣事實上在兩岸關係中扮演相當獨立且重要之角色。因為實證證據顯示，僅有中國對臺的衝突／合作程度，會以互惠模式回應臺灣對中行為，但是臺灣對中的衝突／合作程度，卻不受於中國對臺行為之影響；第二，中國和臺灣互動行為的正向發展，都將引發雙方行為的不穩定。

What is the relationship between cross-strait relations and the U.S.-China-Taiwan triangle? The question has implications in both theoretical and political areas. This paper aims to answer these questions with statistical analysis based on event data from 1979 to 2012. First, does the United States play a role in cross-strait relations? Second, if the answer is yes, in what way does the United States influence the behaviors of Taiwan and China? In general, this paper examines how a certain state behavior in the U.S.-China-Taiwan triangle influences cross-strait interactions. The result shows that the leverage of the United States in cross-strait relations is in fact very limited and has worked in an indirect way since 1979. First, the United States can influence China's negative-or-positive behavioral pattern toward Taiwan by changing China's calculation of utility toward Taiwan. Second, Taiwan's behavior toward the United States can influence the stability of Taiwan's behavior toward China. Third, two bilateral patterns between Taiwan and China are also evident. First, only China's negative-or-positive pattern responds to Taiwan in a tit-for-tat way. Taiwan, on the other hand, does not respond to China's behavior with any pattern. Thus, Taiwan in fact plays an active and independent role in cross-strait relations. Second, any positive development of Taiwan and China's behaviors toward each other in fact leads to instability for both sides of the Taiwan Strait.