Polymarket and Kalshi disagree on their definitions, highlighting the issue of "definition accuracy" in prediction markets amid the US government shutdown.

With the US Congress failing to complete the full legislative process for its appropriations bill, the US government is expected to enter a short-term, partial shutdown starting Saturday (Eastern Time). However, this event also highlights the issue of contract definition precision in prediction markets. Prediction contracts on Polymarket and Kalshi regarding "whether the government will shut down" show discrepancies due to different trigger condition definitions. Polymarket's contracts show an approximately 88% probability of a government shutdown, while similar contracts on Kalshi show a probability as high as approximately 93%. This may be because some contracts use whether the US Office of Personnel Management (OPM) officially declares a shutdown as the settlement basis, even if it's only a partial shutdown. This event underscores the high sensitivity of prediction markets to contract trigger conditions, official confirmation entities, and timing in political and macroeconomic events; contract details themselves have become a significant factor influencing odds. (CoinDesk)