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Why spreads get tighter over time, and why that matters.

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The Problem Alpha Decay Solves

When a market first opens, nobody knows anything. The crowd hasn’t spoken yet. If spreads are tight from the start, a single whale can move prices dramatically and snipe cheap shares before anyone else has a chance. But if spreads stay wide forever, the market never becomes efficient. Traders get bad prices even when the market is mature and well-informed. Alpha decay solves both problems at once.

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How It Works

Alpha (α) is the liquidity parameter that controls how much prices move per trade. Think of it as the market’s “shock absorber.” 
High α → Prices barely move per trade (wide shock absorber)
Low α  → Prices move a lot per trade (stiff shock absorber)
With alpha decay, the market starts with a high α and gradually decreases it: 
Day 1:  α = 3,333  (wide spreads, whale-resistant)
Day 3:  α = 2,500  (moderate spreads)
Day 5:  α = 1,667  (tighter)
Day 7:  α = 1,000  (tight spreads, efficient pricing)

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A Day in the Life of a Market

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Morning: The Market Opens

BTC 24-hour market opens
α = 3,333 (high)

Alice bets $500 on $96K-$97K
Price moves: barely (0.3%)

This is by design — early info is noisy.
No one should dominate the price with one bet.

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Afternoon: The Crowd Arrives

α has decayed to 2,000

Same $500 bet now moves price 0.5%
Market is starting to form real opinions
Spreads are tighter, better deals for traders

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Evening: Market Matures

α = 1,000

The probability distribution is well-formed
Prices are responsive. Good info gets rewarded.
Spreads are tight. Fair pricing for everyone.

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The Result

Early bettors got paid a premium for betting with less information (wider spreads = better odds for contrarians). Late bettors get efficient prices that reflect the crowd’s wisdom.

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Why Traders Should Care

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Early Bird Premium

Alice bets at α = 3,333: Gets 6x odds on her range
Bob bets same range at α = 1,000: Gets 3.5x odds

Same prediction. Alice got paid more for betting first.
This is intentional. Alpha decay rewards conviction. If you have an edge, bet early.

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Late Game Efficiency

By the time α is low, prices are tight.
You see what the crowd actually thinks.
Great for spotting mispriced ranges.

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Why LPs Should Care

Alpha decay directly benefits LPs through surplus harvesting. 
Market opens: α = 3,333
Required reserves: $9,240

Market matures: α = 1,000
Required reserves: $2,772

Surplus released: $6,468
→ Vault harvests this → LPs get capital back early
The Vault doesn’t have to wait for resolution to start recouping capital. As α decays, the excess safety margin is returned.

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The Settings

Market creators configure alpha decay at creation:
ParameterWhat It Does
Initial αStarting liquidity depth
Final αFloor (spreads never go tighter than this)
Decay startWhen decay begins (e.g., 2 hours after open)
DurationHow long until α reaches the floor
Example:
Initial α = 3,333
Final α = 1,000 (can't go below 30% of initial)
Start: 1 hour after market opens
Duration: 6 hours

→ Spreads narrow linearly over 6 hours

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The Bottom Line

Alpha decay is the difference between a dumb market and a smart one. It starts cautious and ends precise.

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Next Steps

LMSR ExplainedUnderstand the pricing algorithmLMSR Explained
The VaultHow LPs benefit from alpha decayThe Vault