Rival: light weight, not youth, carries the marathon handicap chase lift

Reasoning

Why this hypothesis exists: what the lab saw, the question it asked, the mechanism it proposed, what it predicted, and the result that would prove it wrong. Written before the test was run.

1. Observed
   • H-9cf148a1 (Older horses in marathon handicap chases are over-bet (mirror of the y) pointed the predicted way but failed the bar: A/E 0.97 on 148 bets (p 0.581), control 1.03. O-0ba01528
   • H-8b0e3766 (Rival: big-field festival marathon handicaps, not youth, produce the l) passed discovery but was falsified: driven by one price band (up to 7/1): the rest score 0.89; 2 of 3 attacks broke it; fewer than two periods with enough bets to compare (thin: the forward record will judge). O-7c17994b
   • H-98848406 (Young marathon chasers stepping up to 3m4f+ for the first time carry t) met the sealed vault supportive: A/E 1.22 on 384 bets (p 0.0945, threshold 0.0025). O-bef6da89
2. AskedIs the young-stayer lift at 3m4f+ a weight effect, with young, lower-rated horses carrying light weights over trips where every pound counts more? answered
3. MechanismOver 3m4f+ the effect of weight builds up over the extra distance and the tiring finish. Young chasers are usually lower-rated and carry light weights, so the lift credited to age may really belong to a light weight.
4. Why the market misses itPunters price on rating and form, and the weight scale treats a pound the same at 2m and at 4m. If weight counts for more at marathon trips, light weights are under-bet whatever their age.
5. Predictedpositive, A/E 1.08 to 1.18 on 400+ bets if the rival is real

Mechanism and rationale

Over 3m4f+ the effect of weight builds up over the extra distance and the tiring finish. Young chasers are usually lower-rated and carry light weights, so the lift credited to age may really belong to a light weight.

The rule

race_type = 'Chase' AND is_handicap = 1 AND age >= 8 AND distance_yards >= 6160 AND weight_lbs <= bottom_weight_lbs + 7

Reads: race_type, is_handicap, age, distance_yards, weight_lbs, bottom_weight_lbs

Pre-registration

Spec hash (sha256 of the canonical pre-spec)

c1efa7bb4e5ec2f9b9233a83e5cbd6c8dd995c6b64109e62866fe1fc6e514565

Frozen

not frozen

The definition can still change.

Confounders

• Older light-weights are often out of form or declining horses whose low marks reflect regression, which would push A/E down and hide a weight effect
• Horses running from out of the handicap carry the minimum weight but are effectively overweighted on merit; they fall inside the 'within 7 lb of bottom weight' band and may dilute it
• bottom_weight_lbs may reflect the minimum weight or a claimer's allowance rather than the handicap's true floor, so 'light' is measured relative to the race, not to the scale
• Field size: big fields spread weights wider and change how many runners qualify per race
• Festival marathons (Grand National, Scottish/Welsh/Irish Nationals) have compressed or unusual weight ranges and big-priced fields
• Longshot drag: earlier findings show poor ROI in older marathon chasers came from 16/1+ runners, so the price mix can mask a mid-price effect

Control

{
  "description": "Same-race control: the other runners in these marathon handicap chases should sit near par or below (roughly 0.90-1.00), since they are mostly heavier-weighted horses. The key comparison group separates weight from age: older (8+) horses higher in the weights in the same kind of race. If weight drives the lift, these should score clearly lower than the light-weights (around 1.0 or below); if both groups are similar, weight is not the driver. Compare against the young marathon system (about 1.18): a rival that explains the lift should bring older light-weights close to that figure.",
  "rule": "race_type = 'Chase' AND is_handicap = 1 AND age >= 8 AND distance_yards >= 6160 AND weight_lbs > bottom_weight_lbs + 7"
}

Discovery result

fail broad rule · 16 Oct, 13:58

Bets

124

4 winners

A/E

0.48

95%: 0.13 to 1.22

SP return

-82.9%

level stakes

Betfair SP return

-79.6%

124 bets with a BSP

Strike rate 3.2%. p = 0.97. Same-race control: the other runners in these races had A/E 1.15, so the selection did not beat its own races. Zone: discovery. Evaluator eval-1.0, data 6a4e98be18e83933

Falsification

No attacks yet. Only promising ideas are attacked.

Sealed holdout (vault)

Not queried. Only a frozen idea can spend its one query against the 2020-25 holdout.

Forward record

No forward record. Shadow tracking starts after the vault and counts only races run after the freeze.

Lineage

Agent runs

• designer v1ok · 42s · 16 Oct, 13:56

  Output (schema-checked)

  {
    "rule": "race_type = 'Chase' AND is_handicap = 1 AND age >= 8 AND distance_yards >= 6160 AND weight_lbs <= bottom_weight_lbs + 7",
    "refinements": [
      {
        "label": "14/1 or shorter",
        "rule": "race_type = 'Chase' AND is_handicap = 1 AND age >= 8 AND distance_yards >= 6160 AND weight_lbs <= bottom_weight_lbs + 7 AND sp_decimal <= 15"
      },
      {
        "label": "ages 8-9 only (excludes declining veterans)",
        "rule": "race_type = 'Chase' AND is_handicap = 1 AND age >= 8 AND age <= 9 AND distance_yards >= 6160 AND weight_lbs <= bottom_weight_lbs + 7"
      }
    ],
    "control": {
      "description": "Same-race control: the other runners in these marathon handicap chases should sit near par or below (roughly 0.90-1.00), since they are mostly heavier-weighted horses. The key comparison group separates weight from age: older (8+) horses higher in the weights in the same kind of race. If weight drives the lift, these should score clearly lower than the light-weights (around 1.0 or below); if both groups are similar, weight is not the driver. Compare against the young marathon system (about 1.18): a rival that explains the lift should bring older light-weights close to that figure.",
      "rule": "race_type = 'Chase' AND is_handicap = 1 AND age >= 8 AND distance_yards >= 6160 AND weight_lbs > bottom_weight_lbs + 7"
    },
    "pass_criteria": {
      "min_bets": 300,
      "min_ae": 1.05,
      "max_p": 0.05
    },
    "forward_bar": {
      "min_bets": 100,
      "min_ae": 1,
      "max_p": 0.2
    },
    "confounders": [
      "Older light-weights are often out of form or declining horses whose low marks reflect regression, which would push A/E down and hide a weight effect",
      "Horses running from out of the handicap carry the minimum weight but are effectively overweighted on merit; they fall inside the 'within 7 lb of bottom weight' band and may dilute it",
      "bottom_weight_lbs may reflect the minimum weight or a claimer's allowance rather than the handicap's true floor, so 'light' is measured relative to the race, not to the scale",
      "Field size: big fields spread weights wider and change how many runners qualify per race",
      "Festival marathons (Grand National, Scottish/Welsh/Irish Nationals) have compressed or unusual weight ranges and big-priced fields",
      "Longshot drag: earlier findings show poor ROI in older marathon chasers came from 16/1+ runners, so the price mix can mask a mid-price effect"
    ],
    "mechanism": "At 3m4f+ the cost of weight adds up over the extra distance and the tiring finish, so a pound matters more than the standard scale assumes. Young marathon chasers tend to be lower-rated and carry light weights, so the live young-stayer lift (A/E about 1.16-1.22) may belong to weight, not age. If so, older horses within 7 lb of bottom weight in the same races should beat their prices too.",
    "market_miss": "Punters and the handicapper price on rating and form using a weight-for-lengths scale that treats a pound the same at 2m and 4m. If weight counts for more at marathon trips, light weights are under-bet whatever their age, and the market blames their low weight on lack of ability, not on a stamina advantage.",
    "prediction": {
      "direction": "positive",
      "size": "A/E 1.08 to 1.18 on 400+ bets if the weight rival is real",
      "falsified_if": "A/E at or below 1.0 on 300+ bets, or the light-weight group not clearly above the heavier older control, which rules the weight rival out and leaves youth as the driver of the marathon lift"
    },
    "notes": "This is a rival-explanation test for the live SYS-young-stayer-marathon-handicap-chase. A null or negative result supports youth as the driver, which is a useful outcome either way. I raised min_bets to 300 to match the falsification threshold. Refinements come from the reasoning: the longshot drag in earlier older-horse results and the 'declining horses' confounder. The price split is not to be sliced further."
  }

Timeline

1. Job 1723 finished

   16 Oct, 13:58 · engine:compute-1

2. H-ebbea470 Discovery → KILLED fails: 124 bets, needs 300; A/E 0.477, needs 1.05; p 0.9673, needs 0.05 or lower; periods [0.4], each needs 1.0; A/E 0.477 against same-race control 1.154, needs 0.03 above (not a niche pass: A/E 0.477 below 1.05; p 0.9673149946517685 above 0.5; does not beat the same-race control 1.154; a period points the other way [0.4])

   16 Oct, 13:58 · engine:evaluator

3. discovery result for H-ebbea470 (broad rule): fail

   16 Oct, 13:58 · engine:evaluator

4. H-ebbea470 Designed → RESEARCHdiscovery measuring on the discovery zone

   16 Oct, 13:58 · engine:orchestrator

5. compute-1 took job 1723 (evaluate, attempt 1)

   16 Oct, 13:58 · compute-1

6. Job 1721 finished

   16 Oct, 13:57 · engine:ai-1

7. Queued evaluate on the compute lane: discovery run of the broad rule

   16 Oct, 13:57 · engine:scheduler

8. H-ebbea470 Proposed → RESEARCHdesigned pre-spec written and hashed

   16 Oct, 13:57 · agent:designer@v1

9. ai-1 took job 1721 (design, attempt 1)

   16 Oct, 13:56 · ai-1

10. Queued design on the ai lane: write the pre-spec

    16 Oct, 13:56 · engine:scheduler

11. New idea H-ebbea470: Rival: light weight, not youth, carries the marathon handicap chase lift (rival-explanation)

    16 Oct, 13:56 · agent:investigator@v1

Every change is an event with an actor: an agent and its version, an engine, a human, or the importer. Current stage: Killed.