Blockchain's economic value lies in enabling financial and economic transactions without relying on trusted, centralized intermediaries. In practice, however, transactions pass through a fragmented chain of intermediaries before being included on-chain. Because standard blockchain data reveal only the winning block, this process is largely unobservable. We address this limitation by constructing a novel dataset of 15,097 non-winning Ethereum blocks, that is, blocks proposed but not selected for inclusion. We show that 21% of user transactions are delayed: they appear in candidate blocks but not in the winning block, implying that fragmented routing materially affects inclusion time. We further show that execution quality varies substantially across candidate blocks: for the same swap, both execution probability and execution price differ across proposed blocks. To study these differences, we examine competition between two arbitrage bots trading between decentralized and centralized exchanges. We find that, conditional on inclusion in a block that also contains transactions from these bots, user swaps in the same (opposite) direction are less likely (more likely) to execute and receive worse (better) prices. These results show that routing and block composition are central determinants of execution quality and market quality in on-chain markets.

翻译：区块链的经济价值在于能够在不依赖可信中心化中介的情况下实现金融和经济交易。然而，在实践中，交易在被纳入链上之前需经过碎片化的中介链条。由于标准区块链数据仅显示获胜区块，这一过程基本不可观测。我们通过构建包含15,097个非获胜以太坊区块（即被提议但未被选中的区块）的新数据集来解决这一局限性。研究发现，21%的用户交易存在延迟：它们出现在候选区块中但未进入获胜区块，这意味着碎片化路由会实质性地影响纳入时间。我们进一步证明，候选区块之间的执行质量存在显著差异：对于同一笔交换，不同提议区块的执行概率和执行价格均不相同。为研究这些差异，我们考察了在去中心化交易所与中心化交易所之间套利的两个套利机器人之间的竞争。实验表明，当用户交易与这些机器人的交易被纳入同一区块时，相同方向（相反方向）的用户交换执行可能性更低（更高）、执行价格更差（更好）。这些结果表明，路由和区块组成是链上市场执行质量与市场质量的核心决定因素。