Replication Data for: The Effect of Candidate List Position on Vote Share: Improving Internal Validity and Expanding Scope Conditions

Objective: When a candidate occupies a favorable position on a ballot, such as the top, they tend to secure a larger share of votes. Nonetheless, identifying position effects is challenging unless these positions are determined exogenously. I intend to improve the internal validity and expand the scope conditions of position effects analyses.

Method: The Japanese House of Councilors election offers an ideal natural experiment for internal validity because candidate positions are randomized across municipalities. Moreover, this case expands the scope conditions of position effects because (1) candidate names are displayed not on a ballot but on a list at the voting booth; (2) voters read the list from right to left and from top to bottom, thus making the top-right corner, rather than the top-left corner, the best position; and (3) the electoral system is a single nontransferable vote system, which has not yet been studied.

Results: When a candidate is located at the top-right corner, the vote share is 0.560 percentage points greater than when they are located in another position. I cannot confirm other position effects.

Conclusion: The results suggest the primacy effect, namely, that the top position increases a candidate's vote share in Japan.

研究目标：若候选人在选票上占据诸如首位这类有利位置，通常可获得更高的得票率。然而，除非位置由外生因素决定，否则识别位置效应颇具难度。本研究旨在提升位置效应分析的内部效度，并拓展其适用范围。
研究方法：日本参议院选举可为位置效应分析的内部效度验证提供理想的自然实验场景，原因在于候选人的名单位置在各市町村选区中均为随机分配。此外，该案例可进一步拓展位置效应的适用范围，具体体现在以下三点：其一，候选人姓名并未印制在选票上，而是展示于投票站内的选举名单中；其二，选民阅读该名单的顺序为从右至左、自上而下，因此最优位置为右上角而非左上角；其三，本次选举采用迄今尚未有相关研究探讨过的单一非转移投票制（single nontransferable vote system）。
研究结果：当候选人处于名单右上角位置时，其得票率较其他位置的候选人高出0.560个百分点；未观测到其他显著的位置效应。
研究结论：本次研究结果验证了首因效应（primacy effect），即在日本参议院选举中，首位位置可提升候选人的得票率。