Method
About
This site treats a rule change as a first-class object with a cause, a date, a citation, and a measurable consequence. The consequence is often that a number series stops being continuous, and that is the part nobody records systematically.
It also says what the rules are now. Each covered sport has its laws in force written out against nine questions asked in the same order of every sport — and each clause links to the recorded changes that produced it, so the current law reads as the output of the timeline rather than as facts that were always true.
Read-only, static, and built for its author to read. There is no ranking of sports against each other and no live data.
One layer is not sourced and is labelled as such wherever it appears: the learning curve for each sport, which answers how hard it is to start and how hard it is to be good at. Those are the author’s verdicts on a five-point scale, never a score out of ten and never summed or averaged, and every piece of evidence under them says whether it is a rule on this site, a checkable observation, or an estimate.
What it refuses to do
- 01
Draw a line across a break
Segments are separate paths on separate scales with a visible gap, and each prints its own axis. No interpolation, no trend line, no shared baseline. This is the whole point of the feature and it is enforced in the data layer, not by convention.
- 02
Invent a citation
Every rule change needs a real edition and article. Where the article has not been confirmed against the text, the entry renders as incomplete rather than being quietly finished.
- 03
Infer a cause
A cause comes from a stated reason or a sourced account. Where sources disagree the cause is disputed and both readings are kept, because a governing body’s stated reason and the widely-believed reason are often different and the gap is the interesting part.
- 04
Pass a scoped series off as the sport’s
Football’s goals per game is labelled with its competition in the chart title itself, not in a footnote.
- 05
Let the skeleton layer borrow the deep layer’s authority
Sports with no rule research show status and classification only and are marked as not yet covered wherever they appear.
Each of these is enforced where the data is shaped, not where it is drawn, so a future chart cannot opt out of one by accident.
The cause vocabulary9
Closed, and carried by shape rather than colour — colour is already carrying sport family, and eleven hues on one screen destroyed that reading. Shape also survives greyscale and colour-blind viewing.
- Safety
- Changed to reduce risk of injury or death to competitors or spectators. Frequently follows a specific incident, which belongs in trigger.
- Broadcast and pacing
- Changed to make match length predictable, shorten dead time, or fit a scheduled slot. The dominant cause of scoring rewrites from the 1990s on.
- Dominance suppression
- Changed after a period in which one nation, athlete, or tactic won consistently enough that the governing body legislated against it.
- Equipment and technology
- Changed because an implement, surface, or garment outran the rules written for it. Usually the cause of the most total comparability breaks.
- Fairness and eligibility
- Changed to define who may compete, in what category, or under what qualification.
- Commercial
- Changed to serve sponsorship, ticketing, or the commercial interests of the governing body, distinct from broadcast scheduling.
- Participation and access
- Changed to widen or narrow who plays the sport, including the addition of women's events and the lowering of entry barriers.
- Integrity
- Changed in response to match-fixing, doping, deliberate underperformance, or the manipulation of judging.
- Disputed
- Sources give conflicting reasons. Both readings are recorded in trigger and neither is presented as settled. Rendered in unmarked.
The four lenses
- Official
- The IOC's own sport-level grouping, as published per Games. It is one sport to one lane and grows a lane for every sport added, which is the whole argument for the other two lenses: this one can tell you what a sport is called and nothing about what kind of thing it is. Switch to Adjudication and eighteen lanes become four. AquaticsAir sportsArcheryAthleticsBadmintonBasque pelotaBaseballBasketballand 67 more, one per sport
- Game category
- The invasion / net and wall / striking and fielding / target grouping from the Teaching Games for Understanding literature, where it originates. It was written to classify games, so it has nothing to say about combat sports, performance events or multi-discipline ones. Four of the sports here fall outside it entirely, and the board shows that lane rather than forcing them into a box. Net and wallInvasionStriking and fieldingTargetPerformanceOutside this taxonomy
- Adjudication
- How the winner is determined. This is the lens that answers the question the timeline exists to ask: do judged sports change their rules for different reasons than measured ones? MeasuredJudgedDecided by scoreCombatSelf-officiated
- Standing
- How a sport holds its place. Eighteen of the thirty-seven sports on the 2028 programme have been removed from it and brought back at least once, which is the single most surprising number on this site: a place on the programme is not a settled thing, and the rule changes that follow a removal read differently once you know that. Never offRemoved, restoredAdded and keptAdmitted, droppedLapsed pre-1940Never Olympic
Where it is incomplete
Coverage grows where the author’s curiosity goes, and the site says so plainly rather than implying completeness. 75 sports have researched rule changes; 350 rule changes and 74 series are recorded, and 75 have their laws in force written out.
Those law summaries carry the same standing as the citations, and the same warning: the figures were entered from the named edition but have not been checked against its text line by line. They are this site’s reading of the laws and not a substitute for them, which is why every one of them links to the rulebook itself.
Two of those series carry no figures. Football’s goals per game and badminton’s match statistics both could exist as scoped series and neither has been assembled from a cited source, so both state that in place of a chart rather than being filled in from recollection. Gymnastics is the different case: there, no series can exist at all.
Most citations name the right edition without a confirmed article number. Every one of those renders as incomplete, and the sources page counts them.