本研究探討台灣在2018年與2021年的兩次公投從同時選舉到非同時選舉的制度改變，產生的投票率變化。本文發現，與大選脫鉤後，公投投票率與青年人口比的相關方向出現逆轉：2018年，青年人口比較高的地區投票率較高；2021年則是青年人口比較低的投票率較高。此外，高教人口比與縣市的執政黨做為本研究之控制變數，控制後，青年人口比與投票率仍維持逆轉。當公投不綁大選後，青年人口比越高，投票率越低；而高教人口比對投票率則不顯著；對比非民進黨執政縣市的投票率變化，2021年民進黨執政縣市則是顯著的增加，代表公投大選脫鉤，執政黨反而積極動員；同意票的分析則顯示了投票率促進同意票，但在脫鉤一般選舉降低投票率下，同意票比例也跟著下降。

This study examines the shifts in voter turnout during Taiwan’s two referenda in 2018 and 2021, resulting from the transition from concurrent elections to separate ones. The research reveals a relationship between referendum turnout and the percentage of young voters when they are no longer held concurrently with general elections. In 2018, regions with a higher proportion of young voters experienced higher participation in referenda, whereas in 2021, areas with a lower percentage of young voters displayed increased turnout. Furthermore, even after controlling for the level of higher education among the population and the political party in power at the town levels, an inverse relationship between the proportion of young voters and turnout remained consistent. When referenda were decoupled from general elections, a higher percentage of young voters was associated with lower overall turnout, and the relationship between higher education and turnout was found to be insignificant. When comparing changes in turnout between cities not governed by the Democratic Progressive Party (DPP), a significant increase in turnout was observed in DPP-led areas in 2021. This suggests that when referenda were decoupled from general elections, the ruling party became more proactive in mobilizing voters. Furthermore, an analysis of approval votes indicates that higher turnout encourages more approval votes. However, in the context of reduced turnout during nonconcurrent elections, the proportion of approval votes also decreased accordingly.

投票成本; 同時選舉; 公投參與; 投票率; 青年人口

cost of voting, concurrent elections; referendum participation; voter turnout; youth population