The prediction market industry had another major week of growth from Aug. 31 to Sept. 6.
Activity was driven by the start of college football, important US Open tennis matches, speculation around central bank policy, and major global esports events.
Combined weekly contract volume across Kalshi and Polymarket Global reached $12.88 billion, a 14.2% increase week over week.
Kalshi continued to grow rapidly, reaching a new multi-week high of $11.86 in contract volume, up 16.7% week over week. That gave Kalshi 92.2% of the combined contract volume across the two platforms. Polymarket Global recorded $1.01 billion, down 8.4%.
In the regulated US market, Polymarket US reported $974.55 million in official Daily Market Report trading volume, an 8.8% increase week over week. Kalshi and Polymarket Global together handled 77,932,024 completed trades, up 3.4% week over week.
| Venue | Contract Volume (Aug 31–Sep 6) | WoW Growth | Combined Market Share | Execution-Price USD | Total Trades | Supporting Open Interest | Active Markets |
|---|---|---|---|---|---|---|---|
| Kalshi | $11,864,848,718 | +16.7% | 92.2% | $3,153,240,806 | 67,429,365 | 759,496,755 | 120,485 |
| Polymarket Global | $1,010,720,807 | -8.4% | 7.8% | $501,156,401 | 10,502,659 | 189,868,531 | 210,933 |
| Polymarket US | $974,546,765 | +8.8% | N/A (Venue-only) | N/A | N/A | 123,969,122 | N/A |
| Combined / Total | $12,875,569,525 | +14.2% | 100.0% | $3,654,397,207 | 77,932,024 | 1,073,334,408 | 331,418 |
Top market drivers and trading catalysts
Trading activity during Aug. 31-Sept. 6 was mainly driven by three areas: Grand Slam tennis, the opening weekend of college football, and expectations around interest rates and the broader economy.
Kalshi: Tennis, college football, and multi-leg Combos
Kalshi’s biggest markets were largely tied to major sports events and rapidly growing combination markets:
- Grand slam tennis: The US Open match between Mariano Navone and Novak Djokovic was Kalshi’s biggest individual market, generating $35.76 million in contract volume. Other major tennis matches included Alexander Zverev vs. Quentin Halys ($30.81M), Alexander Zverev vs. Lorenzo Sonego ($27.68M), Francisco Comesana vs. Flavio Cobolli ($21.90M), and Ben Shelton vs. Denis Shapovalov ($16.73M).
- College football kickoff: The opening slate of college football games generated very high trading activity. Major games included Boise State vs. Oregon ($23.59M), Colorado vs. Georgia Tech ($23.47M), and UCLA vs. California ($17.50M).
- Cross-category combos: Multi-leg combination markets also grew quickly. A 12-leg European football combination featuring Bayern Munich, Leverkusen, Leipzig, and other teams generated $18.21 million, while an eight-leg sports combination covering NFL and city markets generated $17.56 million. Overall, Kalshi’s combination-market volume increased 32.5% week over week to $1.73 billion.
Polymarket Global: Monetary policy and global esports
Polymarket Global showed a different trading pattern, with its biggest markets focused on economic policy and international esports competitions:
- September Fed decision: Trading around the Federal Reserve’s upcoming interest-rate decision was Polymarket Global’s largest individual market. Volume rose 67.8% week over week to $32.83 million.
- Esports dominance: Five of Polymarket Global’s top 10 markets were League of Legends LCK Playoff matches. The biggest esports market, Hanwha Life Esports vs. T1, generated $10.80 million. It was followed by BNK FEARX vs. Dplus KIA ($9.74M), T1 vs. Dplus KIA ($8.61M), Gen.G vs. Hanwha Life ($7.89M), and KT Rolster vs. Dplus KIA ($7.57M). A Counter-Strike match between Spirit and MOUZ also generated $6.47 million.
- Premier League soccer: English Premier League games also generated significant international trading volume. The largest markets were Aston Villa vs. Arsenal ($11.05M) and Everton vs. Manchester United ($8.51M).
Polymarket US: Strong focus on sports
Polymarket US trading was heavily concentrated in sports. The biggest contracts included Navone vs. Djokovic ($6.25M), Colorado vs. Georgia Tech ($5.59M), Zverev vs. Halys ($5.04M), Zverev vs. Sonego ($4.64M), and UCLA vs. Cal ($4.00M).
The $57 billion NFL forecast, industry scale
With the NFL regular season beginning, prediction markets are entering a potentially transformational period of growth. Research from DeFi Rate estimates that Kalshi’s NFL trading volume could reach $56.51 billion during the 2026-27 season under a conservative baseline scenario. That would be nearly eight times the $7.21 billion recorded during the 2025-26 season. Under a stronger growth scenario, volume could reach $128.14 billion if the current pace of preseason trading continues.
Projected Kalshi NFL volume breakdown (2026-27 season)
Total baseline target: $56.51 billion
- 75.2% — Moneylines & Direct Winner Markets: $42.48 billion
- 18.0% — Derivatives (Spreads, Totals, In-Play): $10.19 billion
- 3.1% — Long-Horizon Futures & Season Awards: $1.75 billion
- 1.9% — NFL-Weighted Combination Markets: $1.10 billion
- 1.8% — Player Props & Game Specials: $0.99 billion
Before Week 1 even begins this Thursday, NFL preseason contracts have already generated $621.4 million in volume. DeFi Rate estimates $2.55 billion in trading during Week 1 alone, which would bring cumulative volume to $3.17 billion. Weekly volume is projected to peak at $3.47 billion in Week 13, before reaching $1.97 billion on the Super Bowl.
Long-term trends
Looking at the six completed weeks from Aug. 2 through Sept. 6, the market positions of the major venues changed noticeably:
- Kalshi’s steady expansion: Kalshi grew from $8.42 billion in the week ending Aug. 2 to $11.86 billion in the week ending Sep. 6. Its market share also increased steadily, from 88.3% to 92.2%.
- Polymarket Global contraction: Polymarket Global reached a high of $1.24 billion during the week ending Aug. 23 before falling to $1.01 billion by the week ending Sep. 6.
- Polymarket US momentum: PMUS increased gradually from $866.8 million in early August to $974.5 million during the week ending Sep. 6.
| Week Ending | Aug 2 | Aug 9 | Aug 16 | Aug 23 | Aug 30 | Sep 6 |
|---|---|---|---|---|---|---|
| Kalshi | $8.42B | $8.07B | $8.67B | $9.06B | $10.17B | $11.86B |
| Polymarket | $1.11B | $1.01B | $1.11B | $1.24B | $1.10B | $1.01B |
| Polymarket US | $0.87B | $0.85B | $0.82B | $0.88B | $0.90B | $0.97B |
Smaller markets growing rapidly, Brazil presidential election
Comparing DeFi Rate data from the three most recent completed weeks (Aug. 17-Sep. 6) with the previous three weeks (July 27-Aug. 16) shows several smaller market categories growing quickly:
- 15-minute commodity contracts (Kalshi): Volume jumped 433%, from $58.6 million to $312.1 million. Gold was the main driver, followed by WTI crude oil, silver, copper, and natural gas.
- September Fed rate outcome cluster (Polymarket): Total trading in this group of markets more than doubled, increasing 102% from $32.2 million to $65.1 million. Most trading focused on contracts predicting a 25-basis-point rate cut or no change.
- YouTube view count markets (Kalshi): Volume increased 101%, from $1.5 million to $3.1 million. These markets included daily top-video rankings and weekly artist view-count targets.
- Weather and city temperature markets: Volume rose 39%, from $8.7 million to $12.0 million. Daily rain and high-temperature markets in Miami were the biggest contributors.
- AI model leaderboards: Volume grew 22%, from $624,000 to $761,000. Trading centered on Kalshi’s September “Best AI Model” contract, which compares models such as Google’s Gemini against competing AI systems.
- Global political wildcards: Polymarket also saw significant growth in less traditional political markets. For example, Brazil presidential-election markets involving candidates Pablo Marçal and Augusto Cury generated several million dollars in trading activity.
Category volume breakdown
Looking across the major categories shows that the platforms have developed different areas of strength:
| Category | Kalshi Volume | Polymarket Global Volume | Polymarket US Volume | Combined K + PMG Volume | Kalshi Share | Polymarket Share |
|---|---|---|---|---|---|---|
| Sports | $3,185,551,516 | $356,096,547 | $554,492,053 | $3,541,648,063 | 89.9% | 10.1% |
| Crypto | $1,888,944,146 | $186,210,862 | $225,621 | $2,075,155,009 | 91.0% | 9.0% |
| Economics / Finance | $197,911,684 | $45,585,954 | $1,077,358 | $243,497,638 | 81.3% | 18.7% |
| Politics | $30,893,956 | $50,652,703 | $1,290,227 | $81,546,659 | 37.9% | 62.1% |
| Culture / Entertainment | $4,361,141 | $5,042,982 | $316,498 | $9,404,123 | 46.4% | 53.6% |
| Combos (Non-additive) | $1,732,047,422 | $6,158,696 | N/A | $1,738,206,118 | 99.6% | 0.4% |
| Other / Uncategorized | $6,557,186,276 | $367,131,759 | $417,145,008 | $6,924,318,034 | 94.7% | 5.3% |
Kalshi holds a very large majority of the market in Sports (89.9%), Crypto (91.0%), and Combos (99.6%). Polymarket Global, however, remains stronger in international Politics, where it holds 62.1% of combined political contract volume.
As NFL Week 1 gets underway, prediction markets appear positioned for another major increase in trading activity. The growing volume across sports, finance, politics, and other global events is strengthening their role as real-time forecasting markets.
