Welcome back, football.
The global prediction markets industry saw a surge in activity the week of Sept. 7-13. Trading was boosted by the start of the NFL regular season, major US Open tennis matches, esports playoff series, and continued interest in the upcoming Federal Reserve interest rate decision.
Combined contract volume across Kalshi and Polymarket Global increased 9.3% from the previous week to $14.10 billion, up from $12.90 billion. The total number of trades also grew 10.7% to 86.50 million.
Kalshi continued to dominate the market. It recorded $12.98 billion in weekly contract volume, up 9.4% from the previous week, giving it 92.1% of the combined contract volume of the two platforms. Polymarket Global also improved, rising 7.6% to $1.11 billion and holding 7.9% of the combined market.
Polymarket US recorded $818.52 million in contract volume across the five available daily reports for the week.
As of Sept. 13, the amount of open interest — the total number of contracts still active — was also substantial: 677.18 million contracts on Kalshi, 321.34 million on Polymarket Global, and 164.19 million on Polymarket US.
Football, US Open tennis dominate sports trading
Sports contracts were the biggest source of retail trading activity on prediction market apps during the week.
Kalshi and Polymarket Global together generated $3.76 billion in sports contract volume. Kalshi accounted for $3.265 billion, up 2.2% from the previous week, while Polymarket Global saw sports volume jump 104.7% to $498.81 million. Polymarket US reported another $406.61 million in sports contract volume across its five posted daily reports.
On Kalshi, NFL football games dominated the biggest individual markets. The game between New England and Seattle was Kalshi’s highest-volume sports market of the week, generating $57.86 million in contract volume.
Major college football games also attracted enormous trading activity. Ohio State vs. Texas generated $51.91 million, SMU vs. Florida State generated $39.85 million, and Louisville vs. Ole Miss generated $28.44 million.
Other NFL games also produced large volumes. The San Francisco 49ers vs. Los Angeles Rams game generated $45.30 million, Washington vs. Philadelphia generated $28.48 million, and Green Bay vs. Minnesota generated $24.91 million.
Tennis was another major source of activity as the US Open reached its final stages. The quarterfinal match between Ben Shelton and Carlos Alcaraz generated $40.36 million on Kalshi, $13.02 million on Polymarket US, and $7.01 million on Polymarket Global.
The Frances Tiafoe vs. Alex Michelsen match generated another $35.83 million on Kalshi, $9.09 million on Polymarket US, and $7.01 million on Polymarket Global.
League of Legends playoffs ignite Polymarket Global esports
One of the most notable developments of the week was the rapid growth of esports trading on Polymarket Global. League of Legends playoff matches became some of the platform’s most heavily traded markets, with four different League of Legends matches ranking among its seven biggest individual markets of the week.
The LCK playoff series between Hanwha Life Esports and T1 generated $10.84 million in contract volume. The Gen.G vs. Hanwha Life Esports match generated another $10.79 million during its first week of trading. In China’s LPL playoffs, Anyone’s Legend vs. Invictus Gaming attracted $10.17 million, while Bilibili Gaming vs. Anyone’s Legend generated $6.94 million.
Together, these four esports markets generated more than $38.74 million in weekly volume on Polymarket Global. The results show that the platform is attracting significant international trading activity around competitive gaming, in addition to traditional sports.
Traders continue to bet heavily on the Federal Reserve
Outside of sports, the Federal Reserve’s upcoming interest rate decision was the biggest individual driver of trading activity.
Polymarket Global’s “Fed Decision in September?” market was the highest-volume non-sports market across the entire industry. It generated $48.85 million in contract volume, up 48.8% from $32.83 million the previous week.
As traders positioned themselves ahead of the Federal Open Market Committee meeting, interest-rate markets attracted a growing amount of liquidity on Polymarket Global.
This helped Polymarket Global maintain a strong position in political and economic markets. In politics, Polymarket Global accounted for 72.4% of the combined volume, with $95.72 million, up 12.9% from the previous week. Kalshi accounted for the remaining 27.6%, with $36.41 million, up 17.8%.
In economic markets, Kalshi remained the larger platform, generating $192.45 million, although that was down 2.8% from the previous week. Polymarket Global’s economic volume, meanwhile, jumped 44.0% to $24.95 million.
Multi-leg ‘combo’ markets continue to grow
Another important trend on Kalshi was the continued growth of multi-part “combo” contracts. These allow traders to combine several predictions into one position.
Kalshi’s non-additive combo volume increased 11.1% from the previous week to $1.93 billion. That represented almost the entire combined combo market of $1.95 billion, giving Kalshi a 99.4% share.
One example was a newly launched combo involving five NFL player rushing or receiving performance predictions: Omarion Hampton, David Montgomery, Javonte Williams, De’Von Achane, and Saquon Barkley each reaching 100 yards or more.
That single combo generated $36.44 million in contract volume, making it Kalshi’s sixth-largest individual market of the week.
Weekly and long-term trends
Looking at the broader six-week period from Aug. 9 through Sept. 13, Kalshi has recorded five consecutive weeks of higher volume:
- Week ending Aug. 09: $8.069 billion (88.9% combined share)
- Week ending Aug. 16: $8.671 billion (88.7% combined share)
- Week ending Aug. 23: $9.064 billion (88.0% combined share)
- Week ending Aug. 30: $10.170 billion (90.2% combined share)
- Week ending Sep. 06: $11.865 billion (92.0% combined share)
- Week ending Sep. 13: $12.983 billion (92.1% combined share)
Over those six weeks, Kalshi’s weekly volume increased 60.9%. Its share of the combined market also rose from 88.0% in late August to a record 92.1%.
The number of trades followed the same general trend. Kalshi went from 57.38 million trades in early August to 76.16 million trades in the week ending Sept. 13, an increase of 12.9% from the previous week.
September’s month-to-date numbers make Kalshi’s momentum even clearer. Through Sept. 13, Kalshi had recorded $23.45 billion in contract volume. That was 53.4% higher than the same period in August.
Kalshi’s average completed week in September was $12.98 billion, which was 44.4% higher than its August full-week average of $8.99 billion.
Polymarket Global stabilizes and rebounds
Polymarket Global’s six-week trend shows that the platform appears to have stabilized after a late-August slowdown.
Weekly volume peaked at $1.24 billion during the week ending Aug. 23. It then fell for two consecutive weeks, reaching $1.11 billion for the week ending Aug. 30 and $1.04 billion for the week ending Sept. 6.
The Sept. 7-13 week reversed that trend. Volume increased 7.6% to $1.11 billion.
Through Sept. 13, Polymarket Global had generated $2.00 billion in contract volume, up 4.6% compared with August 1-13.
Its average completed week in September was $1.114 billion, almost exactly matching its August full-week average of $1.116 billion.
Category comparison and sector dynamics
Looking across the major market categories shows clear differences between the platforms:
- Sports ($3.76 billion combined Kalshi and Polymarket Global): Kalshi generated $3.27 billion, giving it 86.7% of the combined volume. Polymarket Global generated $498.81 million, or 13.3%. Polymarket US added another $406.61 million across five reported days.
- Crypto ($1.92 billion combined Kalshi and Polymarket Global): Crypto trading declined modestly on both platforms. Kalshi volume fell 7.5% to $1.75 billion, while Polymarket Global fell 6.5% to $175.75 million. Kalshi held a 90.9% share of crypto contract volume.
- Economics and finance ($217.40 million combined Kalshi and Polymarket Global): Kalshi generated $192.45 million, giving it an 88.5% share. Polymarket Global generated $24.95 million, but its volume jumped 44.0% from the previous week, helped by interest in the Federal Reserve’s upcoming rate decision.
- Politics ($132.13 million combined Kalshi and Polymarket Global): Polymarket Global remained the clear leader, generating $95.72 million, or 72.4% of combined volume. Kalshi generated $36.41 million, or 27.6%.
- Culture and entertainment ($6.82 million combined Kalshi and Polymarket Global): Trading declined on both platforms. Kalshi generated $2.84 million, down 36.9%, while Polymarket Global generated $3.98 million, down 22.3%. Polymarket Global held 58.4% of the category.
The week of Sept. 7-13 highlighted the major forces currently driving growth in prediction markets. Football season is providing Kalshi with a steady stream of extremely high-volume markets, while Polymarket Global is finding strength in esports, economic events, and international political markets.
