Marc's Blog Rugby counterfactuals ยท 1871โ€“2023
A Monte Carlo history

Raeburn Shield, replayed.

What if some Test matches had never happened? Remove a share of rugby history, replay the lineal championship, and see which nations' fortunes change.

The experiment

Edit history at random.

Every simulation independently removes each recorded Test in the selected years with the probability you choose. Scores never change; only the set of matches does.

Small omissions can reroute the Shield for decades. Run the same counterfactual many times to reveal a distribution rather than one lucky timeline.

5%
Each Test has this independent chance of being omitted.
CountriesAll 10 selected
Every Test involving an unselected country is excluded before random removals.
Each simulated run starts with a uniformly selected included country. The unmodified reference keeps the historical holder.

Ready to replay 2,727 Tests from 1871โ€“2023.

Simulation results

Fortunes across selected nations.

Rows are ordered by median successful defences. Bars show the complete simulated distribution; the number beneath is the 10th / median / 90th percentile.

Luck factor: the percentile occupied by each nation's unmodified selected-country-model defences within the chosen year range.
NationUnmodified modelSimulated medianLuck factor
Raeburn Shield simulation distributions by nation Histograms of longest defence streaks, total successful defences, and successful acquisitions.
simulation frequency unmodified selected-country modelAll three columns use their own shared scale across displayed nations.

Official-history acquisition cross-check

The complete lineal history includes three holders absent from the simulation source: Romania, Samoa, and Japan. These acquisition totals follow the Raeburn Shield holder sequence through the model cutoff of 15 July 2023; Scotland's initial 1871 award is not counted as an acquisition. This fixed cross-check does not change with the selected years or countries.

Successful acquisitions in the complete Raeburn Shield history through 15 July 2023.
NationAcquisitions
New Zealand41
South Africa33
Australia30
England28
Ireland23
Scotland17
Wales17
France16
Argentina2
Japan2
Romania1
Samoa1
Italy0
Simulation over time

Lines show the simulated median at sampled year ends; thin whiskers span the interquartile range. Dotted lines show the unmodified model.

simulation median 25thโ€“75th percentile unmodified model

Cumulative successful challenges

A successful challenge is a victory over the current holderโ€”the same event counted above as an acquisition.

Cumulative successful challenges Simulated median cumulative successful challenges with interquartile-range whiskers.

Cumulative retentions

A retention is a holder win or drawโ€”the same event counted above as a successful defence.

Cumulative retentions Simulated median cumulative Shield retentions with interquartile-range whiskers.
Method & data

What this does, and what it doesn't.

Longest streak is the greatest number of consecutive successful defences during one tenure. A draw counts as a defence, as it does under the usual Shield rule.

Successful defences counts every retained challenge across the whole timeline. Acquisitions counts victories over the current holder; the initial award is not an acquisition.

Removing matches is a deliberately simple counterfactual. It does not model changed team strength, selection, travel, scheduling, or the knock-on effects a missing Test would have caused.

The seed makes a run reproducible. Tests are removed using a seeded pseudo-random generator in your browser. No data leaves this page.