The rule
A runner is a DOB if its lowest in-play traded price (Betfair's IPMIN) is half its Betfair Starting Price or lower: IPMIN ≤ BSP ÷ 2.
A runner only counts (“qualifying”) if its BSP is 2.02 or more (half of 2.02 is 1.01, Betfair's minimum price) and Betfair recorded an in-play low for it.
The data
- Source: Betfair's free daily Starting Price files for UK and Irish win markets, promo.betfair.com/betfairsp/prices. A file named for a date holds the previous day's racing.
- Window: 9 Nov 2025 – 9 Nov 2026, from 732 files (UK and Ireland). Updated daily.
- 119,164 runners in 12,948 races. Of those, 115,385 qualify. 2,175 had a BSP under 2.02 and 1,596 had no in-play low recorded (Betfair writes IPMIN as 1001 with a blank IPMAX when nothing qualifying traded in-play, and we treat that as missing).
- Duplicate rows (same race and horse) are dropped. Runners with no BSP are left out.
- Horses are identified by Betfair's selection ID, not their name. Horse pages need 8+ qualifying runs.
Important limits
IPMIN and IPMAX only count bets with a payout over £100. Smaller bets at a lower price aren't reflected, so the in-play low isn't tick-perfect. A runner could have traded at half its BSP in small amounts and still not count, or vice versa.
Version 1 doesn't show when in the race the price dropped. We know whether it halved, not whether that was at the start, halfway or the final furlong.
- BSP is a benchmark, not your price. Anyone trading takes a pre-off price that may differ from BSP.
- Traded isn't matched-for-you. A price trading doesn't mean every order at that price was filled.
- History, not prediction. These are frequencies from the window above. They aren't tips and don't say what will happen next.
Other measures
- Losers that hit ½: among beaten qualifying runners, the share that were a DOB. Winners nearly always trade at or near 1.01, so this measure removes their effect.
- Win rate: share of qualifying runners that won.
- Low ÷ BSP: the in-play low as a percentage of BSP.
- Rates are hidden where there are fewer than 30 qualifying runners, and pages with under 300 get a small-sample warning.
Race types
| Group | Rule (from Betfair's race name) |
|---|---|
| Hurdle / Chase / Bumper / Flat | Race name contains “Hrd” → hurdle; “Chs” → chase; “NHF” or “INHF” → bumper (NH Flat); otherwise Flat. |
| Handicap | “Hcap” anywhere in the name (including novice, listed and graded handicaps). |
| Nursery | Flat “Nursery” (2-year-old handicap). |
| Graded & Listed / Group & Listed | “Grd1–3”, “Grp1–3” or “Listed” and not a handicap. |
| Novice & Maiden (hurdles), Novice & Beginners (chases), Maiden & Novice (flat) | “Nov”, “Mdn”, “Beg”, “Juv”, “Intro” or “Grad” and not a handicap or graded. |
| Hunter & Cross-Country Chase | “Hunt” or “XC” chases. |
| Selling & Claiming | Flat “Sell” or “Claim”. |
| Other | Anything left, such as conditions races. |
Distance bands
The distance at the start of the race name (for example “2m4f”) is converted to furlongs. Flat: 5f–6f, 7f–1m, 1m1f–1m5f, 1m6f+. Jumps (hurdles, chases, bumpers): up to 2m1f, 2m2f–2m5f, 2m6f–2m7f, 3m+. Yards round to the nearest half furlong.
Months
Months use the race date. The first and last months in the window are usually part-months.
Corrections
If a number looks wrong, check the source CSV linked on the runner's row. We take the file as published by Betfair.
The Dobbing Report
Each week: which courses, race types and horses traded at half their BSP in-running, straight from Betfair's own files. Numbers, not tips.