Stale Line
A stale line is a betting price that hasn't been updated to reflect new information. The line is "stale" because it's based on old data while the true probability has shifted. Stale lines are free money for bettors who spot them first.
What Makes Lines Stale
Lines become stale when information changes faster than odds update:
Breaking news. A starting quarterback is ruled out. Sharp books adjust instantly. Slower books take minutes or hours—that gap is a stale line.
Market moves. Sharp money moves the line at one book. Other books haven't updated yet. The lagging books have stale lines.
Live betting. Game situations change by the second. Any delay in live odds creates staleness.
Off-market hours. Books that post lines early may not update overnight. Monday morning lines can be stale relative to Sunday night information.
Exploiting Stale Lines
Professional bettors build systems to capture stale lines:
Real-time feeds. Subscribe to injury news, weather updates, and line movement alerts. Seconds matter.
Multi-book access. Accounts at 20+ sportsbooks let you compare lines instantly and hit the stale one.
Automation. Some sharps use algorithms to detect price discrepancies and execute bets before humans can react.
The edge from stale lines is pure CLV: you're betting at a price that's about to move.
Stale Lines in Prediction Markets
This concept is directly relevant to what we're building at PriceArb.
On Kalshi and other prediction markets, prices should reflect all available information. But they don't always. When a market hasn't updated to reflect:
- Live game state changes
- Breaking news
- Historical probability data
...the price is stale relative to true value.
Our live edge dashboards are designed to detect exactly this: when market prices haven't caught up to what historical data says should be true.
Stale Line Half-Life
Stale lines don't last long:
| Market Type | Typical Stale Duration |
|---|---|
| Pre-game (injury news) | 5-30 minutes |
| Line movement | 1-5 minutes |
| Live betting | Seconds |
| Prediction markets | Minutes to hours |
The more efficient the market, the shorter stale lines survive. Major sportsbooks have reduced staleness dramatically through automated odds engines.
Why Sportsbooks Hate Stale Lines
Stale lines are liability for books. Every stale line is an arbitrage opportunity against them.
This is why:
- Books limit or ban sharps who consistently exploit staleness
- Automated systems update lines faster every year
- Books buy injury/news feeds to stay ahead
The arms race between stale line exploiters and book defenses is constant.
The PriceArb Angle
Traditional stale lines compare current market to other markets. PriceArb finds a different kind of staleness: when current market prices diverge from historical probabilities.
If the market says 30% and history says 45%, the market may be "stale" relative to historical patterns—pricing emotion instead of data.
Explore this on our dashboards.
Related Terms
Ready to Find Edges?
Use our dashboards to spot mispricings and our tools to size your positions.