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Tutorial: Adverse Selection

Difficulty: Phase 2 (Pair Interactions)

Scenario Setup​

You observe aggressive buying on ETH/BTC — trade flow is positive, trade profile shows decent-sized buy orders near mid. Normally this reads as bullish. But the book is telling a different story: supply-side depth is increasing as the buying occurs. Someone is using the buy flow as exit liquidity — selling into the buyers. The buyers are being adversely selected.

Adverse selection is the market's version of a trap: one side's aggression is being used against them.

Observations (Primitive Values)​

Displacement:      +0.05% (mild positive)
Log(A/B):          negative near mid — supply building despite buy flow
Depth:             supply-side resting orders INCREASING as buy flow executes
Trade Flow:        aggressive buying — positive trade imbalance
Trade Profile:     medium trades (500–2K) on buy side near mid
Centroid:          negative — supply-side pressure sits closer to mid than demand
Net Imbalance:     turning more negative over time (supply growing faster than demand)
SLS Gravity:       flat or turning negative — structure NOT confirming the buy flow

Interpretation Engine​

Step 1: Trade flow is positive. On the surface, this is bullish. Buyers are actively lifting offers.

Step 2: But Log(A/B) is negative near mid. Supply is larger than demand at the execution zone. This should not happen during genuine buying pressure — if buyers are consuming supply, supply should be decreasing.

Step 3: Supply-side depth is increasing. Someone is adding supply as buyers consume it. The buyers are providing exit liquidity for a larger seller who is patiently restocking the offers.

Step 4: Centroid is negative — the center of structural pressure favors supply and sits close to mid. The structural pressure is proximate, not distant.

Step 5: SLS gravity is flat or negative. If the buying were genuine structural momentum, gravity would be rising. Its absence means the structure does not believe in the move.

Step 6: The buyers are being adversely selected. They are buying at prices that structure suggests are too high, against a seller who has more capital and patience.

Rule Blocks​

RULE — ADVERSE SELECTION DETECTION:
IF trade flow positive AND Log(A/B) negative near mid AND supply depth increasing
→ buy flow is being absorbed by a larger passive seller
→ buyers are being adversely selected

RULE — ADVERSE SELECTION CONFIRMATION:
IF adverse selection detected AND SLS gravity flat/negative AND centroid negative
→ high-confidence adverse selection — structure confirms the seller, not the buyer

RULE — ADVERSE SELECTION RESOLUTION:
IF buyer flow exhausts (trade imbalance declines toward zero)
→ passive seller has no more exit liquidity
→ price drops as remaining supply overwhelms — the adverse selection was correct

RULE — ADVERSE SELECTION INVALIDATION:
IF buy flow overwhelms supply AND supply depth starts decreasing
→ the initial adverse selection reading was wrong — this is genuine absorption
→ transition to [Absorption → Breakout](/docs/tutorials/absorption-vs-expansion)

Outcome Mapping​

IF buyer flow exhausts and supply remains: The passive seller has successfully distributed into the buy flow. Once buying stops, there is no remaining demand to support the price. The ratio drops — displacement contracts, potentially going negative as the supply overhang pushes price down.

IF buyer flow intensifies and overwhelms the passive seller: The adverse selection thesis is wrong. The buyer has more capital than the seller. Supply depth starts depleting despite restocking attempts. The setup transitions from adverse selection to absorption → breakout.

What Would Invalidate This?​

  • The supply being added is at levels far from mid (not at execution edge) — it is not providing exit liquidity, just structural positioning
  • The buy flow is from liquidation cascades (forced, not voluntary) — both sides are mechanical, not strategic
  • SLS gravity turns positive and accelerates — structure flips to confirm the buyer
  • The supply restocking stops — the passive seller runs out of inventory to distribute

Primitives Used​

  • Trade Flow — aggressive buying (the "victim" side)
  • Trade Profile — size and location of buy trades
  • Log(A/B) Depth — negative near mid despite buy flow
  • Depth — supply increasing during buy flow
  • Centroid — negative, confirming supply proximity
  • Trade Imbalance — positive but diverging from structure
  • SLS — gravity not confirming buy side
  • Displacement — mild positive that structure does not support