README.md

---
license: cc-by-4.0
language:
  - en
pretty_name: Bookmaker Margin Panel
size_categories:
  - 1K<n<10K
task_categories:
  - tabular-regression
  - tabular-classification
tags:
  - sports-betting
  - bookmaker-margin
  - overround
  - gambling-economics
  - panel-data
  - tabular
configs:
  - config_name: default
    data_files:
      - betbetter_margin_panel.csv
      - betbetter_prop_margin_panel.csv
---

# Bookmaker Margin Panel — daily measured betting margins across 22 leagues and 3 market types

A daily panel of **measured bookmaker margins (overround/vigorish)** across head-to-head, spread
and totals markets: one row per day × league × region × market type, aggregated from over
4 million individually recorded odds observations (2.7 million cleaned markets).

To our knowledge this is the only openly published bookmaker margin panel. It quantifies the
*price* of sports betting — the amount by which a market's implied probabilities exceed 100% —
across operators, sports and time.

| | |
|---|---|
| **Files** | Main panel: 3,494 cells (day × league × region × market type × time-to-start) · Props panel: 1,148 cells |
| **Underlying observations** | 2,002,681 cleaned main markets + 699,733 two-sided player-prop markets |
| **Bookmakers aggregated** | 52 (not identified individually — see Limitations; exchanges excluded) |
| **Leagues** | 22 competition keys across 15 sports, including 9 soccer leagues |
| **Market types** | head-to-head (2- and 3-way), spread, total |
| **Period** | 29 June – 2 August 2026, 35 days (collection continues; quarterly updates planned) |
| **Licence** | CC BY 4.0 |

## Columns

| Column | Meaning |
|---|---|
| `snap_date` | Observation date (UTC) |
| `sport` | League/competition key, e.g. `baseball_mlb`, `soccer_epl` |
| `region` | `au`, `us` or `offshore_intl` — the licensing region of the operators aggregated in the cell |
| `market_type` | `h2h`, `spread` or `total` (main panel); specific prop market key in the props file |
| `time_to_start` | Hours from observation to scheduled start, bucketed (under 6h to over 7 days) — main panel |
| `outcomes` | Number of priced outcomes (2, or 3 for soccer-style h2h with the draw) |
| `mean_margin_pct` | Mean margin that day: sum of the outcomes' implied probabilities minus 100, in percent |
| `n_markets` | Number of distinct market observations in the cell (cells with fewer than 10 are excluded) |
| `n_bookmakers` | Number of distinct operators aggregated in the cell |

## Method

For every pre-match market observation, all priced outcomes were converted to implied
probabilities (1 ÷ decimal odds) and summed; the excess over 100% is the margin. Two-way and
three-way markets are kept in separate cells because their margins are not comparable. Excluded:
in-play observations, implausible margins (below 0%, or above 20% two-way / 35% three-way —
suspended or near-settled prices), and betting exchanges.
Full methodology: https://betbetter.world/studies/bookmaker-margins

## Headline findings from this panel

- **Player props average a 7.93% margin — 66% more than main head-to-head markets (4.77%)**.
  To our knowledge this is the first public measurement of prop-market margins (699,733
  two-sided prop markets, MLB/NHL/soccer/basketball prop families).
- The market-type price ladder: h2h **4.77%** &rarr; spreads **4.90%** &rarr; totals **5.45%**
  &rarr; three-way soccer h2h **7.67%** &rarr; player props **7.93%**.
- **Margin has a term structure**: it peaks 1&ndash;3 days before the start (5.23%) and
  compresses to 4.71% in the final six hours — betting early costs measurably more.
- **Australian-licensed bookmakers average 5.25%, US-licensed 4.72%, offshore/international
  4.55%** — Australians pay roughly 11% more margin than Americans for equivalent bets.
- Individual operators are not identified in these files; operator-level statistics (a 3.16% to
  5.78% spread between the cheapest and dearest bookmaker) are published in the accompanying
  study: https://betbetter.world/studies/bookmaker-margins

## Limitations

One month of collection (a longer panel accumulates with each planned update). Individual
bookmakers are deliberately not identified in the files: cells aggregate across all operators in
a region (n_bookmakers reports how many), so no operator's prices or price patterns are
recoverable — the files are irreversible statistics, not a data feed in any form. Head-to-head is
the tightest market type bookmakers offer; margins on multis and player props are materially
higher, so these figures are a floor for the cost of betting generally. No individual odds,
prices or market observations are included — both files are aggregate statistics derived from a
licensed feed that does not permit redistribution of the underlying prices.

## Licence and citation

CC BY 4.0 — free to use, including commercially, with attribution.

> Bet Better (2026). *Bookmaker Margin Panel: daily measured betting margins across 22 leagues,
> three market types and player-prop markets.* https://betbetter.world/studies/bookmaker-margins

Maintained by [Bet Better](https://betbetter.world), which also publishes a
[free sports model API](https://betbetter.world/api/) and an
[open AFL dataset](https://doi.org/10.5281/zenodo.21612783).

> This dataset contains no odds, no prices and no wagering data — aggregate statistics only. 18+.
> Most people lose money gambling. If gambling is causing you harm: gamblinghelponline.org.au.