鑑於國際觀光客的消費支出帶給觀光接受國外匯收入增加與在經濟上產生的乘數效果，觀光事業受到各國之重視，觀光客消費支出之相關議題亦一直受到各國學術單位的關注與研究。鑒於諸多研究皆以最小平方法（OLS）或TOBIT估計旅遊消費支出，忽略旅遊參與需求（去／不去）對旅遊消費支出的影響。若將這兩種決策分開估計，將導致樣本選擇性偏誤而造成估計上的誤差出現。本文採用1999-2003年的「中華民國臺灣地區家庭收入之暨個人所得分配訪問調查」資料，並將旅遊參與需求區分為「國內旅遊參與」與「國外旅遊參與」，利用Heckman二階段迴歸估計法，同時增列不考慮旅遊參與之下OLS與Tobit法分別估計國內與國外旅遊消費支出。研究結果發現，不論是國內旅遊亦或國外旅遊消費支出都會受到國內或國外旅遊需求的影響，因此亦可證實旅遊需求與旅遊消費支出是聯合決定的。

International tourist expenditures can have successive and magnified impacts on a host country's economy and create the induced multiplier effect. Hence, the travel industry is valued highly by all countries and issues regarding travel expenditures have received the greatest attention from scholars. Most previous studies on travel expenditure, which used OLS regression or the Tobit estimator, ignored the effect of travel needs (participant or non-participant) on travel expenditure. If these two categories were analyzed separately, it would result in biased and inconsistent estimates and yield straightforward interpretations. We collected the data for this study from the Taiwan Household survey covering the period 1999-2003 and focused on a sample consisting of 68,470 people. Travel needs were divided into “domestic travel choice” and “outbound choice,” and a two-stage Heckman model was used to evaluate the factors associated with the probability of participation and actual spending, respectively. The OLS and Tobit estimates are also reported to estimate domestic and outbound travel expenditures separately, without taking into consideration the probability of participation. Therefore, we conclude that domestic or outbound travel expenditures are influenced by probability of participation decisions. The results also identify the decision of travel participation and travel expenditures that are jointly made.