Prediction markets continued to see strong growth during the week of Aug. 17-23.
Across Kalshi and Polymarket Global, traders exchanged more than 10.27 billion contracts for $3.36 billion in volume. Trading activity accelerated even faster, with combined trades increasing 7.9% week over week to 77.28 million transactions.
The week’s biggest driver was sports, which accounted for roughly 76.5% of combined volume. Politics and regulatory markets followed at 14.2%, while macroeconomic and pop-culture markets made up the remainder.
| Metric | Kalshi | Polymarket Global | Combined |
|---|---|---|---|
| Contract volume | 9.06B | 1.21B | 10.27B |
| WoW contract growth | +4.5% | +9.6% | +5.1% |
| Execution-price volume | $2.74B | $620.7M | $3.36B |
| WoW execution-dollar growth | +4.0% | +7.7% | +4.7% |
| Trades | 64.14M | 13.14M | 77.28M |
| WoW trade growth | +7.1% | +12.0% | +7.9% |
| Open interest* | 662.4M | 249.9M | — |
| Active markets* | 107,425 | 186,852 | — |
Polymarket US is tracked separately because its Daily Market Reports use a different reporting methodology and do not provide comparable weekly trade-count data.
What drove trading last week?
Sports remained the clear primary engine of prediction-market activity, accounting for approximately $2.57 billion, or 76.5%, of volume.
PGA Tour BMW Championship
The BMW Championship generated significant activity on Kalshi ahead of Thursday’s opening round.
Kalshi’s Top 5, Top 10, and Top 20 finish markets generated more than $200,000 in volume on Wednesday alone. Scottie Scheffler’s Top 5 and Top 10 contracts attracted $303,634.68 in total volume, while Rory McIlroy and Xander Schauffele also drew some action.
European soccer and tennis
European soccer markets were another major source of volume on both platforms. La Liga and Premier League matches generated more than $300 million in combined value.
Tennis also contributed plenty of activity, with US Open tune-up matches producing more than $6.7 million in single-day order flow on Kalshi for some matchups.
Politics remained active
Political markets generated approximately $478 million, or 14.2% of combined volume.
The Michigan Democratic Senate primary was one of the week’s biggest political markets, generating more than $7.5 million in weekly volume across Kalshi and Polymarket US.
Other notable activity included:
- Florida Republican gubernatorial primary: $5.9 million in public-facing trade volume on Polymarket US.
- South Carolina Senate markets: $11.40 million in total execution-price volume across Kalshi and Polymarket Global.
- UK Clacton by-election: $4.79 million in total execution-price volume on Polymarket Global.
Fed and interest-rate markets
Interest-rate markets generated approximately $55.2 million in weekly notional volume.
Traders overwhelmingly expected the Federal Reserve to leave rates unchanged at the upcoming FOMC meeting, with the probability of no change remaining above 97% across the relevant markets.
Taylor Swift leads weekly artist view-count markets
Kalshi saw $257,594.55 in total trading volume across its weekly artist view-count markets.
Taylor Swift led the category with $130,041.24 in total trading volume—$78,689.11 more than Bad Bunny (2.5×; $51,352.13 total), $110,935.14 more than Drake (6.8×; $19,106.10 total), and $115,793.89 more than Ariana Grande (9.1×; $14,247.35 total). Swift accounted for 50.5% of the category’s $257,594.55 in total volume.
Three interesting things from this week’s trading
Looking at contract prices, market density, and open interest reveals some notable differences in how the two platforms are being used.
Traders on Kalshi are trading more low-priced contracts
Kalshi recorded 9.06 billion contracts worth $2.74 billion in volume. That works out to an average execution price of approximately 30.3 cents per contract.
Polymarket Global recorded 1.21 billion contracts and $620.7 million in volume, producing an average of approximately 51.4 cents per contract.
In other words, a larger share of Kalshi’s contract activity happened at lower prices. That helps explain why Kalshi generated significantly more contract volume without the same type of increase in dollar volume.
Polymarket has more markets, but Kalshi concentrates more activity
Polymarket Global had approximately 186,852 active markets, compared with 107,425 on Kalshi.
But the amount of volume generated per active market was dramatically different:
- Kalshi: ~$25,544 per active market
- Polymarket Global: ~$3,322 per active market
The numbers point to two different market structures.
Kalshi’s activity is more concentrated in a smaller number of heavily traded contracts, while Polymarket Global spreads activity across a much larger number of markets.
Kalshi has much higher trading turnover
Kalshi generated roughly 7.5 times more weekly contract volume than Polymarket Global:
- Kalshi: 9.06 billion contracts
- Polymarket Global: 1.21 billion contracts
But its Sunday open interest was only about 2.65 times higher:
- Kalshi: 662.4 million
- Polymarket Global: 249.9 million
That gap suggests substantially more turnover on Kalshi. Traders appear to be entering and exiting positions more frequently, while a larger proportion of Polymarket Global positions remain outstanding relative to the platform’s weekly trading volume.
Week-over-week momentum
The industry continued to expand across the major activity metrics.
| Metric | WoW Change |
|---|---|
| Kalshi trade count | +7.1% |
| Polymarket Global trade count | +12.0% |
| Combined execution-dollar volume | +4.7% |
| Combined contract volume | +5.1% |
| Polymarket US open interest (Aug. 22) | 111.4M |
One notable takeaway is that trade counts grew faster than dollar volume. That suggests the week’s growth was driven in part by increased trading frequency rather than simply larger amounts of capital being deployed.
Broader industry developments
Sweepstakes operators continue moving toward prediction markets
Regulatory pressure on dual-currency sweepstakes gaming continues to push operators toward prediction-market infrastructure.
ProphetX has already moved away from its sweepstakes model and launched its prediction markets platform. And Fliff, through Fliff FCM LLC, recently applied for registration as a Futures Commission Merchant with the National Futures Association.
The developments point to an increasingly blurred line between the sweepstakes and prediction market industries.
Bottom line
The Aug. 17-23 period was another strong week for prediction markets.
The headline numbers:
- 10.27 billion combined contracts traded
- $3.36 billion in combined volume
- 77.28 million combined trades
- +7.9% weekly growth in trade count
- +5.1% weekly growth in contract volume
- Sports accounted for roughly 76.5% of volume
