The Origins of Economic Voting: Investigating Where and When Vote Swings Come From

To accurately understand strategic and economic voting, statistical models of voting behaviour must account for the dynamic and compositional nature of voting data. Using Tandon’s (2012) analysis of voter responses to tariff reforms in India, we illustrate that statistical models that fail to take account of these properties draw inaccurate conclusions about the pattern and motivations behind voting. First, we argue that in panel data voting is a dynamic decision; vote swings in one period affect swings in subsequent periods. The inclusion of lagged values of voting outcomes incorporate these time-dependencies and capture dynamic voting processes. Second, we argue that the adding-up constraint implicit in voting data, showing that a vote swing towards one party must always be offset by a swing away from another party, must be explicitly incorporated into voting behaviour models to avoid bias. We make an important methodological contribution by adapting existing compositional models- intended for modelling vote shares in a single election- to capture changes in vote share between elections and developing diagrammatic tools that support intuitive analysis of vote swings. Once the dynamic and compositional nature of the data is accurately modelled, we show that patterns of economic voting seen in India from 1991 to 2004 are starkly different to those reported in Tandon (2012). Voters exposed to tariff reductions ignored both the social protection offered by the Far Left and the anti-reform sentiments of the BJP, turning instead from the INC to Regional parties.

为精准阐释策略性投票（strategic voting）与经济性投票（economic voting）的内在逻辑，投票行为统计模型必须充分考量投票数据的动态性与构成性特征。本文以坦登（Tandon, 2012）对印度选民针对关税改革的反应所开展的分析为案例，证明若统计模型未纳入上述两类特征，将无法准确揭示投票行为背后的模式与动因。其一，面板数据中的投票行为属于动态决策：某一时期的投票倾向变动会对后续时期的投票倾向变动产生影响。纳入投票结果的滞后项，能够刻画此类时间依赖性，从而捕捉动态投票过程。其二，投票数据中隐含着加总约束：即投向某一政党的选票增量，必然会被投向其他政党的选票减量所抵消，这一约束必须被显式纳入投票行为模型以规避估计偏差。本研究作出了一项重要的方法论贡献：我们对原本用于单选举场景下选票份额建模的现有构成性模型进行适配改造，使其能够刻画选举间的选票份额变动，并开发了可直观分析投票倾向变动的图示工具。当我们精准建模了投票数据的动态性与构成性特征后，研究结果显示，1991年至2004年间印度的经济性投票模式，与坦登（Tandon, 2012）报告的结论截然不同。在关税削减政策影响下的选民，既忽视了极左翼（Far Left）提供的社会保护政策，也未接纳印度人民党（BJP）的反改革立场，转而将选票从印度国民大会党（INC）投向地区政党。