System: Four- and five-year-olds in novice chases

Mechanism and rationale

Few horses are sent over fences this young, and those that are have usually shown their yard they jump. The market prices them as immature horses taking on older, stronger ones.

The rule

race_type = 'Chase' AND is_novice = 1 AND is_handicap = 0 AND age <= 5

Reads: race_type, is_novice, is_handicap, age

Pre-registration

Spec hash (sha256 of the canonical pre-spec)

not designed yet

Frozen

not frozen

The definition can still change.

Backing

bookmaker

Kind

system

Live from

2026-10-13

Matched

{
  "hypothesis_id": "H45-young-horses-in-novice-chases",
  "similarity": 1,
  "variant": "broad"
}

Published

true

Rules

• The race is a novice chase that is not a handicap.
• The horse is four or five years old.

Source

Age analysis, October 2026

System id

young-novice-chasers

Tier

none

Where

race_type = 'Chase' AND is_novice = 1 AND is_handicap = 0 AND age <= 5

Discovery result

Not measured yet.

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

• investigator v1ok · 39s · 16 Oct, 11:05

  Output (schema-checked)

  {
    "reflection": "The thread has not yet shown that a young-chaser edge exists under the lab's yardstick. The imported H45 rule (age 5 or under in non-handicap novice chases) was GREEN at 1.095 on 435 bets. Re-measured here it gives A/E 0.963 on 204. The imported lift also came only from the later periods: the first period was 1.00 on 254 bets.\n\nTwo follow-up tests failed:\n- **Handicap chases (H-ce840402):** young horses came out at 0.967 on 521 bets. Periods were 1.01 and 0.88, and the same-race control was 1.017. GB was 0.973 and Ireland 0.933. This is not a real opposite-direction discovery, because p for the opposite direction is only 0.41. It just says youth alone, over fences, is priced right.\n- **Chase debut (H-fd37b556):** only 11 bets, so it says nothing either way. The other runners in those races came out at 1.139, though. That is a warning sign.\n\nTogether, these point away from \"the young horse is underrated\". The rival worth testing first is that non-handicap novice chases as a race type beat the field-size-corrected yardstick, and young horses only share that. The 16/1+ band in the handicap test (1.18 on 96 bets, 3 wins) is the familiar longshot artefact and is not evidence of anything. The age 4 versus age 5 split should not be run yet: slicing a rule that does not reproduce would break the method rules.",
    "answers": [],
    "questions": [
      {
        "question": "Do all runners in non-handicap novice chases beat the field-size-corrected yardstick, so that H45's imported lift is a property of the race type rather than of age?",
        "rationale": "The handicap generalisation failed: 0.967 on 521, with a same-race control of 1.017 (O-4dc10e5b). So youth does not travel outside novice chases. If older runners in the same novice chases also sit near 1.09, the live system SYS-young-novice-chasers is selecting a race type, not a horse, and needs review. Read race_type, is_novice, is_handicap, age, field_size, sp_rank and book_pct, and split by region and period.",
        "observation_ids": [
          "O-4dc10e5b"
        ],
        "priority": 0.75
      }
    ],
    "hypotheses": [
      {
        "title": "Older horses in non-handicap novice chases match the young ones (race-type rival to H45)",
        "family": "age",
        "operator": "rival-explanation",
        "question_id": null,
        "new_question": 0,
        "parent_id": "H45-young-horses-in-novice-chases",
        "reasoning": {
          "observation_ids": [
            "O-4dc10e5b"
          ],
          "question": "Is H45's lift a property of non-handicap novice chases (small fields, short-priced favourites, unexposed jumpers) rather than of being four or five?",
          "mechanism": "Non-handicap novice chases have small fields and odds-on favourites, and every runner's jumping is largely unknown. A yardstick corrected for field size and price could misprice the whole race type, and young horses would simply inherit that. Young horses beat their price in this race type but not in handicap chases, which fits a race-type effect.",
          "market_miss": "If this is real, it is not something the market misses. It would be a gap in the lab's yardstick for small novice chase fields, which would explain why the import and the lab's re-measurement disagree.",
          "prediction": {
            "direction": "positive",
            "size": "A/E 1.03 to 1.09 on 800+ bets, similar to the young runners in the same races",
            "falsified_if": "A/E at or below 1.00 across the periods while age 5 and under stays higher, which would leave age as the explanation"
          },
          "rule_sketch": "race_type = 'Chase' AND is_novice = 1 AND is_handicap = 0 AND age >= 6"
        },
        "confounders": [
          "field size",
          "odds-on favourites dominating small fields",
          "Festival and graded novice chases",
          "Irish race class unavailable before 2026-07",
          "period effect (the lift was all in later periods)"
        ],
        "expected_survival": 0.3
      }
    ],
    "findings": [
      {
        "statement": "Young horses (age 5 or under) in handicap chases are priced right: A/E 0.967 on 521 bets, periods 1.01 and 0.88, against a same-race control of 1.017. Youth over fences is not an edge in itself outside non-handicap novice chases.",
        "kind": "fails",
        "observation_ids": [
          "O-4dc10e5b"
        ]
      },
      {
        "statement": "The 16/1+ lift in the young handicap-chaser test (1.18 on 96 bets, only 3 wins) repeats the known longshot artefact and should not be read as support for a young-horse trigger.",
        "kind": "method",
        "observation_ids": [
          "O-4dc10e5b"
        ]
      }
    ]
  }

Timeline

1. hypothesis note SYS-young-novice-chasers

   15 Oct, 23:10 · importer

2. New idea SYS-young-novice-chasers: System: Four- and five-year-olds in novice chases (import)

   15 Oct, 23:10 · importer

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