Prediction markets are designed to aggregate dispersed information about future events, yet today's ecosystem is fragmented across heterogeneous operator-run platforms and blockchain-based protocols that independently list economically identical events. In the absence of a shared notion of event identity, liquidity fails to pool across venues, arbitrage becomes capital-intensive or unenforceable, and prices systematically violate the Law of One Price. As a result, market prices reflect platform-local beliefs rather than a single, globally aggregated probability, undermining the core information-aggregation function of prediction markets. We address this gap by introducing a semantic alignment framework that makes cross-platform event identity explicit through joint analysis of natural-language descriptions, resolution semantics, and temporal scope. Applying this framework, we construct the first human-validated, cross-platform dataset of aligned prediction markets, covering over 100 000 events across ten major venues from 2018 to 2025. Using this dataset, we show that roughly 6% of all events are concurrently listed across platforms and that semantically equivalent markets exhibit persistent execution-aware price deviations of 2-4% on average, even in highly liquid and information-rich settings. These mispricings give rise to persistent cross-platform arbitrage opportunities driven by structural frictions rather than informational disagreement. Overall, our results demonstrate that semantic non-fungibility is a fundamental barrier to price convergence, and that resolving event identity is a prerequisite for prediction markets to aggregate information at a global scale.

翻译：预测市场旨在聚合关于未来事件的分散信息，然而当前的生态系统却碎片化地分布在异构的运营商平台和基于区块链的协议上，这些平台和协议独立地列出经济上相同的事件。由于缺乏共享的事件身份概念，流动性无法跨场所汇集，套利变得资本密集或无法执行，价格系统性违背一价定律。因此，市场价格反映的是平台局部的信念，而非单一的、全局聚合的概率，这削弱了预测市场核心的信息聚合功能。我们通过引入一个语义对齐框架来解决这一差距，该框架通过对自然语言描述、结算语义和时间范围的联合分析，使跨平台事件身份变得明确。应用此框架，我们构建了首个经过人工验证的、跨平台的对齐预测市场数据集，涵盖了从2018年到2025年十个主要场所的超过100,000个事件。利用该数据集，我们发现大约6%的事件在多个平台上同时挂牌，并且语义等价的市场即使在高度流动和信息丰富的环境中，也表现出平均2-4%的持续存在执行意识的价格偏差。这些错误定价产生了由结构性摩擦而非信息分歧驱动的持续跨平台套利机会。总体而言，我们的结果表明，语义不可替代性是价格收敛的一个根本障碍，而解决事件身份问题是预测市场在全球范围内聚合信息的先决条件。