本文目的乃研究美國職業棒球大聯盟 (MLB) 自 2012 年開始外卡制度的改變，進入季後賽支隊伍從原本8隊增加為10隊與2012年以前相比，本文推測更多球隊加入而造成之進入季後賽不確定性，將會增加比賽之激烈性，進而使觀眾滿場率增加。本篇文章從蒐集了2002年至2019年大聯盟 30 隊每場比賽資料，並加入其他變數來觀察觀眾滿場率之影響。

本文的實證研究先將資料分成 (2002-2011) 外卡制度改制前，以及 (2012-2019) 外卡制度改制後兩個時期，並利用追蹤資料多元迴歸的方式檢測外卡制度的改變是否能增加觀眾滿場率，結果發現外卡改制無顯著增加主隊之觀眾滿場率。接著再將外卡排名中間靠前的隊伍設定為實驗組，其餘隊伍則為對照組，並利用雙重差分 (difference-in-differences, DID) 來檢定外卡改制後是否能使原本沒有機會進入季後賽的球隊，因為外卡制度的改變而有了進入季後賽的可能，並因此刺激球迷進場增加觀眾滿場率，結果發現外卡制度的改變無法刺激外卡排名中間靠前的隊伍觀眾滿場率顯著增加。

The purpose of this article is to study the changes in the Wild Card system in Major League Baseball (MLB) in the United States since 2012. The changes expanded the number of teams entering the postseason from the original 8 teams to 10 teams compared to before 2012. The article speculates that the increased uncertainty of entering the postseason due to the addition of more teams may intensify the competition and subsequently lead to higher attendance rates among viewers. This study collected game data from all 30 MLB teams from 2002 to 2019 and incorporated other variables to examine the impact on attendance rates.

The empirical research in this article first divides the data into two periods: pre-reform of the Wild Card system (2002-2011) and post-reform (2012-2019). It employs multiple regression analysis on panel data to test whether the changes in the Wild Card system could increase attendance rates. The results indicate that the Wild Card reform did not significantly increase attendance rates for home teams. Next, the teams ranking towards the middle of the Wild Card standings are designated as the experimental group, while the remaining teams serve as the control group. The article employs the Difference-in-Differences (DID) method to examine whether the reform of the Wild Card system could provide previously excluded teams with the opportunity to enter the postseason and consequently stimulate fan attendance. The findings suggest that the reform did not significantly increase attendance rates for the teams ranking in the middle of the Wild Card standings.

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