The information incorporation half-life for high-liquidity Polymarket political contracts is approximately four hours. That single number is one of the most important datapoints in political trading, because it dictates the entire timing of your strategy. Within four hours of a news event, half of the eventual price adjustment has typically occurred. By eight hours, roughly 75%. By sixteen hours, the market has priced in nearly everything the news is going to move. If you're reacting to political news a day late, there's almost nothing left to capture.
What Information Half-Life Means in Practice
Half-life is a concept borrowed from physics, and it applies perfectly to how Polymarket digests information. When a new polling release, a candidate gaffe, an endorsement, or a policy announcement hits, prices begin moving immediately. The initial movement is fast and often overshoots. The subsequent adjustment — reversion from the overshoot toward the "correct" new price — constitutes the remaining price discovery.
The four-hour half-life means the first four hours capture the largest share of the total move. Traders who see the news within minutes and can assess its impact quickly have the best entries. Traders who arrive four hours later are fighting over the second-half of the move, which is smaller and more contested. Traders who arrive the next day are buying or selling at prices that have already fully incorporated the information.
This timing dynamic creates three distinct trading windows around news events in political markets.
The Three Windows
Window 1: The Initial Spike (0-30 minutes)
The first window is dominated by speed traders — people with push notifications from primary data sources who can assess political information quickly and execute trades in minutes. During this window, prices move sharply as early traders pile in, often overshooting the eventual equilibrium.
The risk in this window is execution. Liquidity thins during rapid price moves because market makers pull their orders when volatility spikes. You might identify the correct direction immediately but face wide spreads or insufficient depth to enter at a reasonable price. This window rewards traders with both speed and an existing understanding of the market's pre-news structure.
For most traders, the first window is not their edge. Unless you have a systematic way to receive and process political information faster than the crowd — a dedicated news terminal, expertise in the specific domain, or automated alert systems — competing with the fastest participants in this window is a losing proposition.
Window 2: The Digest (30 minutes - 4 hours)
The second window is where the most consistent edge lives for informed political traders. The initial spike has occurred, but the market is still processing the implications. Traders are debating the significance of the news, secondary analyses are being published, and the price is oscillating as different views compete.
During this window, the price has moved from its pre-news level but hasn't settled at its post-news equilibrium. If you can assess whether the initial spike was an overreaction or underreaction based on your understanding of the political dynamics, you can position profitably.
The key skill in this window is contextual assessment. A polling release showing a 3-point shift looks dramatic in isolation, but if you understand that the poll's methodology tends to overweight a particular demographic, or that the shift is consistent with a broader trend already visible in other data, your assessment of the poll's true informational value will be more accurate than the market's initial reaction.
Window 3: The Fade (4-72 hours)
Empirical analysis of post-news price behavior in Polymarket political markets shows that roughly 60% of the eventual mean reversion happens within 90-120 minutes after the spike. The remaining reversion plays out over 24-72 hours. This creates the fade trade — one of the most well-documented patterns in prediction market trading.
The mechanics of the fade are simple: when news breaks, emotional traders pile into Polymarket, pushing prices past their fundamental value. Once the emotion subsides, prices drift back toward equilibrium. The fade trader waits for the spike, assesses that it's an overreaction, and takes the opposite side.
The Iran Ceasefire market in April 2026 illustrated this pattern clearly. On a ceasefire rumor, prices spiked from 35% to 68% in eight minutes. By hour two, the fundamental situation hadn't changed materially, and the market had settled back to 58%. Over the following 36 hours, it continued reverting. Traders who waited, sold No at 64% and exited at 48%, captured a clean profit from the overshoot.
The critical caveat: approximately half of initial spikes are not overreactions. Sometimes the news genuinely warrants the full price movement, and fading it means selling into a move that continues. The fade only works when you have an independent basis for believing the spike overstates the information's impact. Fading reflexively — without assessing whether the move is justified — is a fast way to lose money.
Data Sources and Speed Hierarchy
The speed at which you receive political information determines which window you can trade in. The hierarchy for political markets looks roughly like this:
Tier 1 (seconds to minutes): Breaking news terminals, official government feeds, primary source data releases. AP, Reuters, and Bloomberg terminals fire alerts before most social media accounts. Direct access to FEC filing databases, court docket systems, and government press release feeds puts you ahead of anyone consuming these through intermediaries.
Tier 2 (minutes to an hour): Curated social media feeds from credible political journalists and analysts. Twitter/X lists of political reporters in specific beats provide fast coverage, but the signal-to-noise ratio is low. Political newsletters with push notifications (Cook Political Report, Sabato's Crystal Ball) are reliable but not instantaneous.
Tier 3 (hours): Media summaries, YouTube analysis, podcast commentary. By the time information reaches this layer, the first and second trading windows are closed. This tier is useful for building long-term analytical frameworks but not for timing individual trades.
The practical implication is that most retail traders should not try to trade the immediate reaction. Their edge, if they have one, is in the digest and fade windows where political understanding matters more than speed.
Event-Specific Half-Lives
Not all information is created equal, and half-lives vary by event type.
Polling releases: Half-life of approximately 2-4 hours. Markets digest polling data quickly because the information is quantitative and easy to interpret. A new poll shifts the RealClearPolitics average by a calculable amount, and traders adjust accordingly.
Candidate announcements (entries, exits, endorsements): Half-life of 4-8 hours. These events require more qualitative assessment — how does this endorsement change the race dynamic? How does a candidate exit reshape the remaining field? The longer half-life reflects the market's need for more time to process the implications.
Policy and regulatory events: Half-life of 6-12 hours. Policy announcements often have complex, indirect effects on political markets. A tariff announcement affects midterm election markets through its impact on consumer prices and economic sentiment, but tracing that chain requires more analytical work.
Scandals and viral moments: Half-life of 1-2 hours for the initial spike, but a much longer tail of uncertainty. Scandal markets often spike quickly and then oscillate for days as new details emerge, making them particularly treacherous to trade.
Building a News-Trading System
A systematic approach to trading political news on Polymarket involves several components:
Pre-position your information stack. Before any specific news event, know which data sources you'll monitor and how quickly you can access them. Set up alerts for the specific markets you trade. Have your Polymarket account funded and ready to execute — scrambling to deposit funds during a news event costs you the entire first window.
Pre-commit to your assessment framework. When news breaks, you need to evaluate its impact quickly. Having a pre-built mental model — "a 2-point polling shift in a battleground state is worth approximately X cents on the chamber control market" — lets you assess faster than someone reasoning from scratch.
Pre-define your entry and exit rules. The fade trade, for example, has specific entry criteria: wait for the initial spike to plateau, assess whether the move exceeds your estimate of the news's fundamental impact, enter if the divergence is large enough to justify the trade after transaction costs, and set a target exit based on historical reversion patterns.
Track your timing accuracy. Over time, measure how accurately your entry timing captures the available price movement. If you're consistently entering after the bulk of the move has occurred, you're trading in the wrong window for your information speed.
Frequently Asked Questions
Is it possible to automate news trading on Polymarket? Yes, Polymarket's API supports automated trading, and some traders build systems that monitor news feeds and execute trades based on predefined criteria. However, the political judgment required to assess news impact is difficult to automate reliably. Most successful automated political traders use semi-automated systems where the news assessment is human but the execution is algorithmic.
How does the half-life differ between high-liquidity and low-liquidity markets? In high-liquidity markets, the half-life is shorter because more traders are watching and competing to incorporate information. In thin markets, price adjustments can take days because fewer participants are paying attention. This creates an opportunity: a national news event might reprice the chamber control market within hours but take a full day to reach an individual race market.
Can the half-life change over time? Yes. As Polymarket attracts more sophisticated participants and more capital, half-lives tend to compress. The median arbitrage window across all market types shrank from 12.3 seconds in early 2024 to roughly 2.7 seconds by 2026. Political markets follow the same trend, though more slowly because political judgment is harder to automate than quantitative arbitrage.
Time Is the Edge
In political markets, time is the scarcest resource. The four-hour half-life means that every hour of delay costs you a measurable fraction of the available edge. The traders who consistently profit from news events aren't the ones with the best political opinions — they're the ones who receive information fastest, assess it most accurately, and execute before the window closes.
Key Takeaways
- Political news has a measurable half-life on Polymarket — roughly four hours before most of the edge is priced in.
- The three windows (instant, hours, days) each call for a different execution approach.
- Your data-source hierarchy determines how fast you receive information relative to the market, and speed is the whole game.
- Arbitrage windows have compressed sharply since 2024, so systematic, low-latency execution matters more every year.
Related guides: correlated-market lag trades · whale tracking on Polymarket — or see what PolyBro is and join the PolyBro waitlist for an autonomous AI agent that researches any Polymarket market for you.