System: Easy winner, out again within a fortnight

Mechanism and rationale

A horse that won with something in hand is better than the winning margin shows, and the margin is all the handicapper has to go on. Running it again within fourteen days is the yard using that before the form is fully reassessed. About level at bookmaker starting price, profitable at Betfair SP. Twelve months of data only.

The rule

last_position = 1 AND last_won_easily = 1 AND days_since_last_run <= 14

Reads: last_position, last_won_easily, days_since_last_run

Pre-registration

Spec hash (sha256 of the canonical pre-spec)

not designed yet

Frozen

not frozen

The definition can still change.

Backing

exchange

Kind

system

Live from

2026-10-13

Matched

{
  "hypothesis_id": "H34-won-easily-last-time",
  "similarity": 1,
  "variant": "back within 14 days"
}

Published

true

Rules

• The horse won its last race easily (from the in-running remark).
• It runs again within 14 days.

Source

In-running remarks, October 2026

System id

easy-winner-back-within-a-fortnight

Tier

none

Where

last_position = 1 AND last_won_easily = 1 AND days_since_last_run <= 14

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 · 42s · 16 Oct, 16:14

  Output (schema-checked)

  {
    "reflection": "The thread has one measurement, and it was imported from earlier research. Last-time winners that won easily scored A/E 1.048 on 2,374 bets, with periods of 1.08 on 1,121 and 1.02 on 1,253. BSP ROI was +2.9% and SP ROI was -12%. Read on its own, that is a weak lift that is fading. All the strength sat in the 14-day split: 1.147 on 597 bets, graded GREEN, while the broad rule is graded RED. That split is now the live system SYS-easy-winner-back-within-a-fortnight. Our current belief is that the 'easy' flag carries little value by itself. Any edge seems to depend on the yard running the horse again before the handicapper or the market catches up. Nothing in this thread has tested that belief yet. The fortnight split was one cut chosen from several, and no rival has been run against it. The two things to check are the obvious rival (quick-returning winners in general) and a consequence that must hold if the mechanism is right (the lift should sit in handicaps, where the mark lags).",
    "answers": [],
    "questions": [
      {
        "question": "Is the lift for easy winners back within 14 days caused by the easy-win flag, or do all last-time winners back within 14 days beat their price?",
        "rationale": "The live system rests on a split. If winners that did not win easily (last_position = 1, last_won_easily = 0, days_since_last_run <= 14) score close to 1.15 as well, the edge comes from the quick return and not from the margin underselling the horse. That would change what the system claims to capture. Columns: last_position, last_won_easily, days_since_last_run, sp_decimal.",
        "observation_ids": [
          "O-65eec625"
        ],
        "priority": 0.75
      },
      {
        "question": "Is the fortnight lift concentrated where the handicap mark has not yet caught up, i.e. handicap to handicap?",
        "rationale": "The mechanism says the handicapper reacts only to the margin, and a quick return can beat the reassessment. The lift should therefore be strongest in handicaps after a handicap win and weak in non-handicaps. Columns: is_handicap, last_is_handicap, days_since_last_run, last_official_rating.",
        "observation_ids": [
          "O-65eec625"
        ],
        "priority": 0.6
      },
      {
        "question": "Is the broad easy-winner lift decaying over time (1.08 then 1.02), and does the 14-day subset show the same decay?",
        "rationale": "The period split for the broad rule is falling. If the fortnight system falls the same way, the live system may be living on an earlier regime. Columns: days_since_last_run, last_won_easily, region, race_type, split by period.",
        "observation_ids": [
          "O-65eec625"
        ],
        "priority": 0.4
      }
    ],
    "hypotheses": [
      {
        "title": "Rival: quick-returning last-time winners beat their price whether or not they won easily",
        "family": "story",
        "operator": "rival-explanation",
        "question_id": null,
        "new_question": 0,
        "parent_id": "SYS-easy-winner-back-within-a-fortnight",
        "reasoning": {
          "observation_ids": [
            "O-65eec625"
          ],
          "question": "Does the 14-day lift belong to the easy-win flag or to quick returns after any win?",
          "mechanism": "A yard that brings a winner straight back is signalling that the horse is well and is exploiting it before reassessment. That could produce the lift with or without an easy win.",
          "market_miss": "The market sees a fresh winner but may underrate how much the yard's intent is worth. If this rival holds, the 'easy' label adds nothing.",
          "prediction": {
            "direction": "positive",
            "size": "A/E 1.08 to 1.15 on 1500+ bets if the rival is true; about 1.00 if the easy flag is the driver",
            "falsified_if": "Winners that did not win easily, back within 14 days, score A/E at or below 1.02 on 1000+ bets, which leaves the easy flag as the cause"
          },
          "rule_sketch": "last_position = 1 AND last_won_easily = 0 AND days_since_last_run <= 14"
        },
        "confounders": [
          "penalty-carrying runners in handicaps",
          "race class of the last win",
          "summer turf calendar density"
        ],
        "expected_survival": 0.35
      },
      {
        "title": "Test-mechanism: easy-winner quick-return lift lives in handicap-to-handicap runs",
        "family": "story",
        "operator": "test-mechanism",
        "question_id": null,
        "new_question": 1,
        "parent_id": "SYS-easy-winner-back-within-a-fortnight",
        "reasoning": {
          "observation_ids": [
            "O-65eec625"
          ],
          "question": "Is the fortnight lift strongest where the mark lags the true ability?",
          "mechanism": "After a handicap win the handicapper reassesses only on the margin, and the new mark or penalty takes days to apply. An easy winner that runs again quickly in a handicap is still well treated.",
          "market_miss": "Punters price the penalty or the new mark as if it fully reflects the win. Because the margin understates the horse's true superiority, the horse is still under-rated.",
          "prediction": {
            "direction": "positive",
            "size": "A/E 1.15 to 1.25 on 250+ bets",
            "falsified_if": "A/E at or below the parent's 1.147, or below 1 in either period"
          },
          "rule_sketch": "last_position = 1 AND last_won_easily = 1 AND days_since_last_run <= 14 AND is_handicap = 1 AND last_is_handicap = 1"
        },
        "confounders": [
          "field size",
          "Flat versus jumps mix",
          "penalised versus re-rated runners"
        ],
        "expected_survival": 0.4
      }
    ],
    "findings": [
      {
        "statement": "Broad easy last-time winners only just beat their price: A/E 1.048 on 2,374, with the period figure falling from 1.08 to 1.02 and SP ROI at -12%. So the easy-win label on its own is mostly priced.",
        "kind": "data",
        "observation_ids": [
          "O-65eec625"
        ]
      }
    ]
  }

Timeline

1. hypothesis note SYS-easy-winner-back-within-a-fortnight

   15 Oct, 23:10 · importer

2. New idea SYS-easy-winner-back-within-a-fortnight: System: Easy winner, out again within a fortnight (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.