本文延伸Gary-Bobo and Trannoy (2015) 競爭市場的學貸模型, 將其 「代表性學生」 的整合式設定修改為「學生之間未整合」, 重新檢視貸款學生的事後效用。 此外也在獨占市場的環境下, 進行相同的分析與比較。 Gary-Bobo and Trannoy (2015) 的結論顯示在充分資訊(最優解) 下, 不同型態學生得到之事後效用完全相等(得到相等待遇), 且認為直到次優解時才出現事後效用不相等的主要原因是資訊不對稱。 然而本文研究結果顯示, 不論是背景為競爭或獨占市場, 資訊不對稱並非不同型態學生事後效用不相等(或事後待遇不相等) 的必要條件; 不同形態學生未整合乃是其事後效用不相等(事後不相等待遇) 的充分條件。 只要不同型態學生之間未進行整合, 則都會得出兩種相異型態學生的事後效用不會是相等的。

The thesis revises Gary-Bobo and Trannoy’s (2015) model of optimal student loans under a competitive market where different types of students are coordinated as a representative one,’ so as to analyze the situation in which uncoordinated students make their own decisions independently under a competitive as well as a monopoly market. Gary-Bobo and Trannoy (2015) shows that different types of students be treated equally and get the same ex post utility under complete information (in the first-best solution), and suggests that they should not be treated unequally and get utilities ex post differently until when information asymmetry is taken into consideration (in the second-best solution). In contrast to the Gary-Bobo and Trannoy’s (2015) model we find out that, while information asymmetry is not the necessary condition to treat different types of students equally so that they have the same utility ex post, a condition of non-coordination between students is sufficient to arrive at the conclusion that different types of students be treated unequally and get utilities ex post differently even under complete information—regardless of the market structure, either competitive or monopoly. That is, it is not the information asymmetry but the condition of coordination between students that counts.

論文審定書 i

摘要 ii

Abstract iii

模型符號對照表 vi

1 緒論 . . . . . . . . . . . . . . . . . . . . . . .1

2 Gary-Bobo and Trannoy (2015) 的學貸模型 . . . . . . . . . . . . . . . . . . . . . . .4

2.1 G-T 模型基本設定 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.2 最優學貸契約的決定 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.2.1 貸款機構部分 . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.2.2 學生部分 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.2.3 最優學貸契約問題 . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.3 關於次優學貸條件 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

附錄 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3 競爭市場的最適學貸契約 . . . . . . . . . . . . . . . . . . . . . . .15

3.1 個別契約之期望利潤為零的競爭均衡. . . . . . . . . . . . . . . . . . . . 16

3.2 廠商總期望利潤為零的競爭均衡 . . . . . . . . . . . . . . . . . . . . . . 18

4 獨占市場的最適學貸契約 . . . . . . . . . . . . . . . . . . . . . . .22

4.1 學生之間有整合的保險條件 . . . . . . . . . . . . . . . . . . . . . . . . 22

4.2 學生之間未有整合的保險條件 . . . . . . . . . . . . . . . . . . . . . . . 24

5 結論與建議 . . . . . . . . . . . . . . . . . . . . . . .26

參考文獻 . . . . . . . . . . . . . . . . . . . . . . .28

中文部分

教育部統計處(2017). 教育統計簡訊, 第82號。 http://stats.moe.gov.tw/files/brief/我
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