{
  "schemaVersion": "vultax-public-research-data-v1",
  "articleUrl": "https://vultax.com/research/kalshi-polymarket-arbitrage-gaps-after-fees",
  "datasets": [
    {
      "title": "Share of readings where a Kalshi–Polymarket gap existed, and where it paid",
      "columns": [
        {
          "name": "Category",
          "unit": null
        },
        {
          "name": "Cleared both venues' fees at depth",
          "unit": "%"
        },
        {
          "name": "Quotes crossed before fees",
          "unit": "%"
        }
      ],
      "rows": [
        [
          "NFL",
          0,
          0
        ],
        [
          "College football",
          0.1,
          3.4
        ],
        [
          "Premier League",
          0,
          0.3
        ],
        [
          "Midterms",
          10.1,
          34.3
        ],
        [
          "Fed decision",
          33.3,
          38.5
        ]
      ],
      "measurementContext": "Five-minute readings, 12–13 September 2026. Sports before kickoff only.",
      "sources": [
        {
          "label": "Kalshi public trade API — events, markets and order books",
          "url": "https://api.elections.kalshi.com/trade-api/v2/events?series_ticker=KXNFLGAME&with_nested_markets=true",
          "note": "Read every five minutes, 12–13 September 2026, with market rule texts"
        },
        {
          "label": "Polymarket Gamma API — events and markets",
          "url": "https://gamma-api.polymarket.com/events/keyset?closed=false&tag_slug=nfl",
          "note": "Markets, fee schedules and rule texts"
        },
        {
          "label": "Polymarket CLOB — order books",
          "url": "https://clob.polymarket.com/books",
          "note": "Bids and asks read in batches every five minutes"
        },
        {
          "label": "Polymarket — trading fees",
          "url": "https://docs.polymarket.com/trading/fees",
          "note": "Per-category taker rates; read 2026-09-12"
        },
        {
          "label": "Kalshi — fee rounding",
          "url": "https://docs.kalshi.com/getting_started/fee_rounding",
          "note": "Trade fees are rounded up"
        },
        {
          "label": "OddsShopper — Kalshi fees",
          "url": "https://www.oddsshopper.com/articles/prediction-markets/kalshi-fees",
          "note": "Third-party statement of the 0.07 taker coefficient"
        },
        {
          "label": "Vultax: Polymarket vs Kalshi midterm odds",
          "url": "https://vultax.com/research/polymarket-vs-kalshi-midterms-odds-2026",
          "note": "Matched midterm contracts and their rules"
        },
        {
          "label": "Vultax: Polymarket sports and esports markets",
          "url": "https://vultax.com/research/polymarket-sports-and-esports-markets",
          "note": "NFL book depth in the six hours before kickoff"
        },
        {
          "label": "Vultax: Kalshi vs Polymarket",
          "url": "https://vultax.com/research/kalshi-polymarket-open-interest-by-category",
          "note": "The venues compared, and the July reading of matched Fed contracts"
        },
        {
          "label": "Vultax: Is Polymarket legal in the US?",
          "url": "https://vultax.com/research/is-polymarket-legal-in-the-us-2026",
          "note": "Which venue U.S. residents can use"
        }
      ],
      "measurement": {
        "kind": "observed",
        "temporalCoverage": "2026-09-12T18:51Z/2026-09-13T22:51Z",
        "population": "26,342 readings of matched contract pairs with both order books, excluding in-play sports",
        "methodology": "Level-by-level walk of the cheaper venue's Yes asks against the other venue's Yes bids, charging each venue's taker fee per level."
      },
      "id": "results-chart",
      "kind": "published-chart",
      "description": "Vultax matched NFL, college football, Premier League, midterm and Fed contracts on Kalshi and Polymarket and walked both order books every five minutes for 28 hours. Midterm gaps cleared both venues' fees in 10% of readings and a Fed longshot in every one; pre-game sports gaps almost never did.",
      "articleUrl": "https://vultax.com/research/kalshi-polymarket-arbitrage-gaps-after-fees",
      "sectionUrl": "https://vultax.com/research/kalshi-polymarket-arbitrage-gaps-after-fees#results",
      "publishedAt": "2026-09-16",
      "modifiedAt": "2026-09-16",
      "version": "b30eb39ef5f98f3f5adb79fcaa0b387d2d81e6f390324a303fd55a33c4eca08b",
      "isLive": false,
      "limitations": "Published research snapshots and calculations; these exports do not contain current quotes or live account data. Observation windows and populations are stated in the source captions and methodology. Missing metadata is unknown, not zero. Figures describe public order books read every five minutes over 28 hours in September 2026. Fee estimates use published or reported rates and exclude rounding, transfers, the cost of capital and settlement risk. Not a recommendation to trade, and not financial advice.",
      "downloads": {
        "json": "https://vultax.com/research/kalshi-polymarket-arbitrage-gaps-after-fees/data.json?dataset=results-chart",
        "csv": "https://vultax.com/research/kalshi-polymarket-arbitrage-gaps-after-fees/data.csv?dataset=results-chart"
      }
    }
  ]
}