When Do Prediction Markets Become Accurate? A Kalshi Political Market Lifecycle Analysis
Are prediction markets accurate? We analyzed 3,195 resolved Kalshi political prediction markets across 25,552 lifecycle snapshots to measure when market odds become reliable.
Prediction markets are usually discussed as if a market price is a clean probability.
A contract trading at 63 cents is treated as a 63% chance.
A contract trading at 92 cents is treated as near certainty.
A contract trading at 5 cents is treated as nearly impossible.
That interpretation is useful.
It is also incomplete.
The deeper question is not only:
Are prediction markets accurate?
The better question is:
When do prediction markets become accurate?
A political market that just opened is not the same as a political market one day before resolution.
A market with two years left to trade is not the same as a market where the final event has mostly played out.
Yet most prediction market analysis treats these prices as if they belong to the same forecasting context.
This analysis uses Kalshi historical data to measure how political prediction market accuracy changes across the life of a market.
We studied:
- 3,195 resolved Kalshi political markets
- 25,552 lifecycle snapshots
- 8 standardized lifecycle checkpoints
- YES prices at each checkpoint
- final resolved YES/NO outcomes
- absolute forecast error
- Brier score
Instead of asking whether political prediction markets are accurate in one static sense, we normalized every market from open to close and measured forecast quality at:
0%, 25%, 50%, 75%, 90%, 95%, 99%, 100%
The result is a lifecycle view of prediction market accuracy.
The main finding:
Political prediction markets are informative from the start, but they become dramatically more reliable as they mature.
At market open, Kalshi political markets already beat a naive 50/50 forecast.
But early market prices still carried large forecast error.
As markets moved toward resolution, error collapsed.
Average absolute error fell from:
34.2 percentage points at market open
to:
1.8 percentage points near market close
Average Brier score fell from:
0.1888 at market open
to:
0.0031 near market close
That means political prediction market accuracy has a timeline.
The Research Question
This study started with a simple question:
How long before political prediction markets become reliable?
There are two common ways to misread prediction market prices.
The first is to dismiss early prices entirely because they are volatile, incomplete, or based on limited information.
The second is to take every quoted price literally from the moment the market opens.
Both views are too simple.
Early political markets may contain useful signal.
But useful signal is not the same thing as high reliability.
A market can beat a naive baseline while still being far less accurate than it will become later.
So the real question becomes:
How quickly does forecast error decline as political markets move from open to close?
That is what this lifecycle analysis measures.
Dataset: 3,195 Resolved Kalshi Political Markets
For this analysis, we used historical Kalshi political markets with known final resolutions.
The working dataset contains:
| Metric | Value |
|---|---|
| Resolved political markets | 3,195 |
| Lifecycle checkpoints per market | 8 |
| Total lifecycle snapshot rows | 25,552 |
| Market type | Kalshi political prediction markets |
| Outcome type | Binary YES/NO markets |
| Forecast column | YES price at checkpoint |
| Outcome column | Final resolved result |
| Forecast metrics | Absolute error, Brier score |
Each market contributes one observation at each lifecycle checkpoint.
For every checkpoint, the analysis selects the latest available YES price at or before that point in the market lifecycle.
That creates a normalized snapshot table.
Conceptually, each market becomes:
| Market | 0% | 25% | 50% | 75% | 90% | 95% | 99% | 100% |
|---|---|---|---|---|---|---|---|---|
| Market A | price | price | price | price | price | price | price | final price |
| Market B | price | price | price | price | price | price | price | final price |
| Market C | price | price | price | price | price | price | price | final price |
That format lets us measure how forecast quality evolves across the lifecycle instead of only measuring final prices.
For a broader guide to accessing and querying historical prediction market data, see:
Kalshi Historical Data — Download, Query, and Backtest
Why Normalize by Market Lifecycle?
Political prediction markets do not all run on the same clock.
Some markets last years.
Others last weeks.
Some resolve after an election, a vote, a court decision, a resignation, a debate, a poll release, a government deadline, or an official certification.
If we compare every market by raw calendar time, we mix together completely different stages of uncertainty.
For example:
- 100 days before close may be early for one market and late for another
- one week after open may be meaningful for a short-duration market and meaningless for a multi-year market
- election night markets behave differently from long-running political outcome markets
- policy markets may remain uncertain until a procedural deadline
- event-driven markets may stay noisy until the final moment
So instead of measuring every market by calendar time, we measured by relative lifecycle position.
Each market was normalized from:
market open = 0%
market close = 100%
Then we sampled market prices at:
0%, 25%, 50%, 75%, 90%, 95%, 99%, 100%
This lets us compare markets with very different durations.
A six-day market and a six-month market can both be analyzed at their 50% lifecycle point.
That creates a cleaner research question:
At the same relative stage of a market’s life, how accurate are Kalshi political prediction market prices?
Methodology: Lifecycle Forecast Error
For each market and lifecycle checkpoint, we selected the latest available YES price at or before that checkpoint.
The forecast probability is:
forecast_probability = YES price / 100
The final resolved outcome is converted into a binary value:
YES outcome = 1
NO outcome = 0
Then we calculate two forecast error metrics.
First, absolute error:
absolute_error = abs(forecast_probability - outcome)
Second, Brier score:
brier_score = (forecast_probability - outcome)^2
These two metrics answer related but different questions.
Absolute error is easy to interpret in percentage-point terms.
If a market says 70% and resolves YES, the absolute error is:
30 percentage points
If a market says 70% and resolves NO, the absolute error is:
70 percentage points
Brier score penalizes larger mistakes more heavily because the error is squared.
That makes it useful for evaluating probabilistic forecasts.
A perfect forecast has a Brier score of:
0
A naive 50/50 forecast has a Brier score of:
0.25
So if the market’s average Brier score is below 0.25, it is beating a naive coin-flip forecast.
Result 1: Prediction Markets Beat 50/50 From the Start
At market open, the average Brier score across the 3,195 resolved Kalshi political markets was:
0.1888
That is meaningfully better than the naive 50/50 baseline:
0.25
This matters.
It means the opening prices were not random noise.
Even at the beginning of the market lifecycle, political prediction markets already contained useful information.
But that does not mean they were highly reliable yet.
At market open, the average absolute error was still:
34.2 percentage points
That is a large error.
So the correct interpretation is not:
early prediction markets are useless.
It is:
early prediction markets contain signal, but they are still noisy.
This distinction is the core of the article.
Prediction market accuracy is not binary.
A market can be directionally informative early and still become dramatically more accurate later.
Result 2: Forecast Error Falls Across the Lifecycle
The clearest finding is the steady decline in forecast error as markets mature.
| Lifecycle checkpoint | Avg absolute error | Avg Brier score |
|---|---|---|
| 0% | 34.2% | 0.1888 |
| 25% | 28.1% | 0.1482 |
| 50% | 21.6% | 0.1115 |
| 75% | 15.2% | 0.0761 |
| 90% | 9.9% | 0.0477 |
| 95% | 7.6% | 0.0359 |
| 99% | 3.8% | 0.0158 |
| 100% | 1.8% | 0.0031 |
This is the core lifecycle result.
At the beginning of the market lifecycle, average absolute error is roughly:
34 percentage points
By the halfway point, it falls to roughly:
22 percentage points
By the 90% lifecycle checkpoint, it falls below:
10 percentage points
By the final checkpoint, it falls below:
2 percentage points
The Brier score tells the same story.
Average Brier score falls from:
0.1888 at market open
to:
0.0031 near market close
That is not a small improvement.
It is a collapse in forecast error.
Chart: Brier Score Across the Political Market Lifecycle
The primary chart for this study is Brier score by lifecycle checkpoint.
This chart should show a clear downward curve from market open to market close.
The visual message is simple:
political prediction market error declines sharply as markets move toward resolution.
The most important interpretation is that the market is already better than 50/50 at open, but not yet highly reliable.
The Brier score starts below the naive baseline:
0.1888 vs 0.25
Then continues falling at every checkpoint.
By the 90% lifecycle checkpoint, Brier score is:
0.0477
By the 99% checkpoint, it is:
0.0158
By the final checkpoint, it is:
0.0031
This is what lifecycle accuracy looks like.
The market does not suddenly become accurate at one magical moment.
It becomes more accurate gradually, then sharply, as uncertainty resolves.
Chart: Average Absolute Error Across the Political Market Lifecycle
Brier score is useful, but average absolute error is easier to explain.
It tells us how far the market’s implied probability was from the final outcome, on average.
This is the most reader-friendly version of the finding:
average forecast error fell from 34.2 percentage points at market open to 1.8 percentage points near market close.
That gives us a practical reliability curve:
Early market: informative but noisy
Mid-life market: materially better
Late market: sharply more reliable
Near-close market: extremely accurate
This is the answer to the search question:
Are prediction markets accurate?
The answer is:
yes, but accuracy depends heavily on where the market is in its lifecycle.
Result 3: The Biggest Accuracy Gains Happen Late
The lifecycle curve is not flat.
Forecast error falls throughout the market lifecycle, but the late checkpoints are especially important.
By 75% of the market lifecycle, average absolute error had fallen to:
15.2 percentage points
By 90%, it fell to:
9.9 percentage points
By 95%, it fell to:
7.6 percentage points
By 99%, it fell to:
3.8 percentage points
That means a large amount of reliability appears late.
This makes intuitive sense.
Political markets absorb information unevenly.
Major information often arrives near key deadlines:
- debates
- candidate announcements
- polling releases
- ballot access deadlines
- legislative votes
- government funding deadlines
- court rulings
- election-night vote counts
- official certification
- public concessions
- market close conditions
A market early in its lifecycle may be forecasting many possible paths.
A market late in its lifecycle is often forecasting a much narrower uncertainty window.
The data reflects that.
The Reliability Timeline
Based on this analysis, Kalshi political prediction market reliability looks roughly like this:
0% lifecycle: market open
The market already contains signal, but forecast error is high.
Average Brier score:
0.1888
Average absolute error:
34.2 percentage points
The market beats a naive 50/50 forecast, but it is still early and noisy.
25% lifecycle
The market improves meaningfully.
Average Brier score:
0.1482
Average absolute error:
28.1 percentage points
There is still substantial uncertainty, but the market is already better than it was at open.
50% lifecycle
The market becomes much more informative.
Average Brier score:
0.1115
Average absolute error:
21.6 percentage points
By the midpoint of the lifecycle, the market has reduced a large amount of early uncertainty.
75% lifecycle
The market enters a more reliable forecasting stage.
Average Brier score:
0.0761
Average absolute error:
15.2 percentage points
This is where the market starts looking less like early speculation and more like a maturing forecast.
90% lifecycle
The market becomes substantially reliable.
Average Brier score:
0.0477
Average absolute error:
9.9 percentage points
At this point, average error is below 10 percentage points.
95% lifecycle
The market is now very late-stage.
Average Brier score:
0.0359
Average absolute error:
7.6 percentage points
The remaining uncertainty is much narrower.
99% lifecycle
The market is near resolution.
Average Brier score:
0.0158
Average absolute error:
3.8 percentage points
Prices are now highly informative.
100% lifecycle
Near the final available checkpoint, forecast error is extremely low.
Average Brier score:
0.0031
Average absolute error:
1.8 percentage points
At this stage, many markets have already converged close to their final outcome.
Do Prediction Markets Get More Accurate Closer to Election Day?
For political markets, the practical version of the lifecycle question is:
Do prediction markets get more accurate closer to election day?
This analysis suggests yes, with one important caveat.
The study does not measure only elections.
It measures Kalshi political markets across a broader set of political outcomes.
But the lifecycle pattern is clear:
as political markets move closer to resolution, forecast error falls dramatically.
That does not mean every individual market becomes smoother or less volatile.
Individual markets can spike, reverse, overreact, underreact, or trade on stale information.
But across 3,195 resolved political markets, the average pattern is strong.
Political prediction markets become more accurate as they mature.
That is the practical takeaway.
Why a 70% Price Means Different Things at Different Times
One of the most important implications is that the same quoted probability can carry different reliability depending on when it is observed.
A 70% price early in a market lifecycle is not equivalent to a 70% price late in a market lifecycle.
The number is the same.
The information environment is not.
Early in the lifecycle, the market may still be pricing:
- unknown candidates
- incomplete polling
- uncertain turnout
- unresolved legal challenges
- incomplete vote counts
- unclear legislative paths
- future negotiations
- ambiguous resolution criteria
- low liquidity
- uncertain trader attention
Late in the lifecycle, many of those uncertainty sources may already be resolved.
So the price may be much more reliable.
This is why prediction market accuracy should not be measured only by the quoted probability.
It should be measured by:
probability + lifecycle position + outcome
A price is not just a probability.
It is a probability at a specific stage of uncertainty.
What Final-Price Calibration Misses
A previous Kalshi political market calibration analysis looked at final traded prices and tested whether high-confidence political markets were overconfident near resolution.
That final-price study found that the expected “90% trap” did not appear.
Final high-confidence political markets were highly reliable at the extremes.
See the related analysis here:
Kalshi Historical Data Analysis: Are Political Prediction Markets Accurate at 90%?
This lifecycle study answers a different question.
Final-price calibration asks:
Are markets reliable near the end?
Lifecycle analysis asks:
How early does that reliability appear?
That distinction matters.
A market can be extremely reliable near completion while still carrying large forecast error early in its life.
This study shows exactly that.
Political markets are useful from the beginning.
But they are not equally reliable at every stage.
Forecast Error vs Calibration
This article focuses on forecast error.
Forecast error asks:
how far was the market price from the final outcome?
Brier score and absolute error both answer that question.
Calibration asks a different question:
when markets say 70%, do they resolve YES 70% of the time?
A market can have falling forecast error and still be miscalibrated in specific probability ranges.
For example, high-confidence markets may become very accurate late in the lifecycle, while early high-confidence markets may still be overconfident.
That is why lifecycle calibration is the natural next layer of analysis.
The key distinction is:
- Brier score measures total probabilistic forecast quality
- Absolute error measures average distance from the outcome
- Calibration measures whether probabilities match observed frequencies
- Lifecycle analysis shows how all of those change over time
Together, they give a much deeper picture of prediction market accuracy.
The Open-Market Accuracy Problem
The most surprising part of the study is not that markets become accurate near resolution.
That part is expected.
The more interesting result is that market-open prices were already better than 50/50.
At 0% lifecycle, the market-open Brier score was:
0.1888
That is substantially below the naive baseline:
0.25
So opening prices contain signal.
But the absolute error was still:
34.2 percentage points
That means early political market prices are useful, but rough.
They are not pure noise.
They are not final truth.
They are early probability estimates under large uncertainty.
This is why the right interpretation is:
early markets are useful inputs, not finished forecasts.
The Near-Close Accuracy Problem
At the other end of the lifecycle, near-close prices become extremely accurate.
At the final checkpoint, average Brier score was:
0.0031
Average absolute error was:
1.8 percentage points
That is extremely low.
But it also needs to be interpreted correctly.
Near-close accuracy can be high because the market has already absorbed decisive information.
For political markets, that might mean:
- election results are already mostly known
- a candidate has conceded
- vote counts are nearly complete
- a bill has effectively passed or failed
- a deadline has expired
- the relevant public information has already resolved the uncertainty
So near-close accuracy does not prove that prediction markets knew the outcome months in advance.
It proves something narrower:
by the end of the lifecycle, political prediction markets are extremely good at recognizing resolved or nearly resolved uncertainty.
That is still valuable.
But it is not the same as long-horizon forecasting power.
Probability Distribution by Lifecycle Checkpoint
Forecast error tells us how close prices were to outcomes.
But another useful chart is the distribution of market prices at each lifecycle checkpoint.
This shows whether markets remain spread across the probability spectrum or begin collapsing toward 0 and 100 as resolution approaches.
This chart is useful because political markets often behave like convergence systems.
Early in the lifecycle, prices may be distributed across a wider probability range.
Late in the lifecycle, markets should increasingly concentrate near:
- near-zero probability
- near-certain probability
That distribution helps explain why late-stage forecast error becomes so low.
The market is not merely becoming “a little better.”
It is often collapsing toward the final outcome.
Market Examples: How Individual Political Markets Converge
Aggregate error curves are powerful, but individual market charts help make the lifecycle intuitive.
A useful companion chart is a single-market or multi-market line chart showing YES price over time for selected political markets.
The goal is not to cherry-pick one perfect example.
The goal is to show the mechanics behind the aggregate result.
Some markets may converge smoothly.
Others may stay volatile until late.
Others may collapse suddenly after a debate, vote count, announcement, or deadline.
That is exactly why lifecycle-normalized analysis is useful.
It lets us compare these very different market paths in a shared framework.
How This Analysis Was Built in Lychee
This analysis was built by combining historical Kalshi political market data with lifecycle-normalized forecast analysis.
The workflow was:
- Filter to resolved Kalshi political markets.
- Normalize each market from open to close.
- Snapshot each market at standard lifecycle checkpoints.
- Extract the latest YES price at or before each checkpoint.
- Convert YES prices into forecast probabilities.
- Convert resolved outcomes into binary values.
- Calculate row-level absolute error.
- Calculate row-level Brier score.
- Aggregate forecast error by lifecycle checkpoint.
- Chart error across the market lifecycle.
The key operations were:
Relative Position Snapshot
→ Forecast Probability
→ Row-Level Forecast Error
→ Lifecycle Brier Score Summary
→ Lifecycle Error Chart
This makes the research reproducible and extensible.
The same approach can be applied to:
- election markets
- policy markets
- sports markets
- weather markets
- economic markets
- crypto prediction markets
- Polymarket data
- Kalshi historical data
The broader point is that prediction market accuracy should not only be measured statically.
It should be measured dynamically across the lifecycle of the market.
Query Kalshi political market data
Search historical Kalshi political markets, lifecycle snapshots, YES prices, final outcomes, and market activity to analyze prediction market accuracy over time.
What This Means for Traders
For traders, the main lesson is that the timing of a price matters.
A market trading at 80% early in its lifecycle should not be interpreted the same way as a market trading at 80% near resolution.
The same probability can represent very different forecast quality.
The data suggests:
- early prices contain signal
- mid-life prices are materially better
- late-stage prices are much more reliable
- near-close prices are extremely accurate
But this does not mean traders should blindly chase late high-confidence markets.
Near-close prices may already reflect information everyone can see.
The edge is not simply knowing that late markets are accurate.
The edge is understanding when the market has not yet fully incorporated information.
What This Means for Researchers
For researchers, the biggest lesson is methodological.
Prediction market accuracy should be tied to time.
A static final-price analysis can make markets look extremely accurate because many outcomes are already nearly resolved by the final trade.
That is not wrong.
But it is incomplete.
A stronger research pipeline asks:
- What was the market price at open?
- What was the market price at 25% of lifecycle?
- What was the market price at 50% of lifecycle?
- What was the market price at 75% of lifecycle?
- What was the market price near resolution?
- How did forecast error change at each stage?
- Did calibration improve at the same rate?
- Did different market categories behave differently?
This turns prediction market commentary into actual quantitative research.
Instead of asking:
are prediction markets accurate?
we can ask:
when, where, and under what market conditions are prediction markets accurate?
That is the better question.
What This Means for Lychee
This is exactly why historical prediction market data matters.
Without historical prices, trade timestamps, market open times, close times, and final outcomes, this kind of analysis is difficult to run.
Kalshi historical data makes it possible to test claims like:
- Are prediction markets accurate?
- How accurate are political prediction markets?
- Do prediction markets get more accurate closer to election day?
- When can you trust prediction market odds?
- Does forecast error decline over time?
- Do high-confidence markets become reliable before resolution?
- Are election markets more accurate than event markets?
- Does volume improve prediction market accuracy?
- Are Kalshi and Polymarket markets calibrated differently?
Lychee is built to make this kind of analysis faster:
- query historical Kalshi market data
- filter by category and resolution
- extract lifecycle snapshots
- calculate forecast error
- compute Brier scores
- build lifecycle charts
- visualize calibration curves
- publish dashboards and charts
- fork the analysis into new markets and categories
This is the core workflow:
turn prediction market history into reproducible market research.
Key Findings
1. Prediction markets beat 50/50 from the start
At market open, Kalshi political markets had an average Brier score of:
0.1888
That beats the naive 50/50 baseline of:
0.25
Opening prices were not random noise.
2. Early political markets are informative but noisy
At market open, average absolute error was still:
34.2 percentage points
So early prices contained signal, but still carried substantial uncertainty.
3. Forecast error declined at every lifecycle checkpoint
Average absolute error fell from:
34.2% at 0% lifecycle
to:
1.8% at 100% lifecycle
The market became progressively more reliable as it matured.
4. Brier score collapsed across the lifecycle
Average Brier score fell from:
0.1888 at market open
to:
0.0031 near market close
That is a major improvement in probabilistic forecast quality.
5. Political markets become substantially reliable late in the lifecycle
By the 90% lifecycle checkpoint, average absolute error had fallen below:
10 percentage points
This suggests late-stage political markets are much more reliable than early-stage markets.
6. Near-close accuracy is extremely high, but should be interpreted carefully
The final checkpoint had extremely low error.
But this likely reflects the fact that many markets have already absorbed decisive information near resolution.
Near-close accuracy is not the same thing as long-horizon forecasting power.
7. Accuracy should be measured through time
The core finding is methodological:
prediction market prices should be interpreted through their lifecycle.
A price is not just a probability.
It is a probability at a specific stage of uncertainty.
Limitations
This study has several important limitations.
Lifecycle position is not the same as calendar time
A market at 50% of its lifecycle could be three days from resolution or three months from resolution.
Lifecycle normalization makes markets comparable, but it does not replace fixed-horizon analysis.
A future study should compare both lifecycle checkpoints and raw time-to-resolution checkpoints.
The 100% checkpoint may reflect near-resolved information
The final checkpoint captures the latest available price near completion.
That price may already reflect information that makes the outcome obvious.
This is useful for studying convergence, but it should not be confused with early forecast skill.
Political markets are heterogeneous
Political markets include elections, policy decisions, speech events, nominations, deadlines, court outcomes, and institutional processes.
Different political market types may have different lifecycle accuracy patterns.
A future version should segment lifecycle Brier score by market type.
This study uses market-count weighting
Each market contributes equally to the aggregate lifecycle score.
That means a small low-volume market and a large high-volume market receive the same weight.
A future study should compare equal-weighted and volume-weighted results.
This study measures forecast error, not every dimension of market quality
Brier score and absolute error measure forecast quality against final outcomes.
They do not directly measure liquidity, spreads, manipulation, market efficiency, trader profitability, or execution quality.
Those require separate analyses.
Future Research
This study opens several follow-up questions.
1. Lifecycle calibration
Measure calibration curves at each lifecycle checkpoint:
- 0%
- 25%
- 50%
- 75%
- 90%
- 95%
- 99%
- 100%
This would show when stated probabilities begin matching observed outcome frequencies.
2. Fixed-horizon forecast accuracy
Measure forecast error at fixed time windows before resolution:
- 90 days before close
- 30 days before close
- 14 days before close
- 7 days before close
- 1 day before close
This would complement lifecycle analysis with calendar-time analysis.
3. Market-type segmentation
Compare lifecycle accuracy across:
- Electoral markets
- Policy markets
- Event markets
This would show whether elections become accurate earlier than high-entropy political event markets.
4. Volume-weighted Brier score
Compare equal-weighted and volume-weighted accuracy.
This would answer whether high-dollar political markets are more reliable than low-volume political markets.
5. Kalshi vs Polymarket lifecycle accuracy
A cross-platform study could compare lifecycle forecast quality across Kalshi and Polymarket.
That would reveal whether accuracy patterns are platform-specific or general to prediction markets.
6. Liquidity and forecast error
A deeper study could test whether spread, volume, trade count, or market depth predicts forecast error.
This would connect accuracy research more directly to trading strategy.
Conclusion
This study began with a question:
When do prediction markets become accurate?
Using Kalshi historical data, we analyzed 3,195 resolved political prediction markets across 25,552 lifecycle snapshots.
The result was clear.
Political prediction markets were informative from the start.
At market open, they already beat a naive 50/50 baseline.
But early prices were still noisy.
Average absolute error at open was:
34.2 percentage points
As markets matured, forecast error declined sharply.
By the 90% lifecycle checkpoint, average absolute error fell below:
10 percentage points
By the final checkpoint, it fell to:
1.8 percentage points
Average Brier score followed the same pattern, falling from:
0.1888 at open
to:
0.0031 near close
The practical takeaway is simple:
Prediction markets become more accurate as they mature.
But the more useful version is:
Political prediction markets are informative early, materially better by the midpoint, and highly reliable late in the lifecycle.
That changes how we should interpret market prices.
A price is not just a probability.
It is a probability at a specific stage of market maturity.
Instead of asking only:
Is this prediction market accurate?
we should ask:
How far through its lifecycle is this market?
That is the lifecycle of prediction market accuracy.
FAQ: Prediction Market Accuracy and Kalshi Political Markets
Are prediction markets accurate?
Prediction markets can be accurate, but accuracy depends on time horizon, market type, liquidity, and information clarity. In this analysis, Kalshi political prediction markets beat a naive 50/50 forecast from market open, but became much more accurate near resolution.
How accurate are prediction markets?
In this lifecycle analysis, average absolute error in Kalshi political markets fell from 34.2 percentage points at market open to 1.8 percentage points near market close. Average Brier score fell from 0.1888 to 0.0031.
Do prediction markets get more accurate closer to election day?
Across 3,195 resolved Kalshi political markets, forecast error declined sharply as markets moved closer to resolution. While the dataset includes more than just elections, the broader pattern suggests that political prediction markets become more reliable as uncertainty resolves.
How accurate are political prediction markets?
Political prediction market accuracy depends on when the market price is observed. Early prices are informative but noisy. Late-stage prices are much more reliable because they have absorbed more information.
Can Kalshi prediction markets be trusted?
Kalshi prediction markets can contain useful forecasting signal, but individual market prices should be interpreted through context. This study shows that Kalshi political markets were informative from the start and became dramatically more reliable as they matured.
What is Brier score in prediction markets?
Brier score measures the squared difference between a forecast probability and the final outcome.
brier_score = (forecast_probability - outcome)^2
Lower Brier scores mean better probabilistic forecasts.
Why use Brier score instead of simple accuracy?
Simple accuracy treats forecasts as right or wrong. Brier score evaluates the quality of a probability. A 55% forecast and a 95% forecast should not be treated the same, even if both resolve YES.
What is forecast error?
Forecast error measures how far a market-implied probability was from the final outcome. In this study, absolute forecast error was calculated at each lifecycle checkpoint.
What is lifecycle analysis?
Lifecycle analysis normalizes every market from open to close, then compares prices at the same relative stage of each market’s life. This allows markets with different durations to be compared more cleanly.
Does this prove prediction markets are better than polls?
No. This study does not directly compare prediction markets against polls. It measures forecast error in Kalshi political prediction markets over time. Polls and prediction markets measure different signals.
Why not only use final market prices?
Final prices can be highly accurate because uncertainty may already be resolved near market close. Lifecycle analysis shows how market accuracy evolves before that final state.
What does Kalshi historical data reveal here?
Kalshi historical data shows that political prediction markets are informative from the beginning, but become dramatically more reliable as they mature. Forecast error falls sharply across the market lifecycle.
Sources and References
- Kalshi Historical Data API Documentation
- Kalshi Market Data Quick Start
- Kalshi Market Data & Insights
- Do Prediction Markets Produce Well-Calibrated Probability Forecasts?
- Duke PDF: Do Prediction Markets Produce Well-Calibrated Probability Forecasts?
- Calibration City: Prediction Market Calibration
- Stable Reliability Diagrams for Probabilistic Classifiers
- Decomposing Crowd Wisdom: Domain-Specific Calibration Dynamics in Prediction Markets
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