|
|
|
|
How to calculate a rating.
Month-by-month analysis of standings.
Frequently asked questions about the table.
Produce potential table based on future matches.
Developed by David Kendix
|
|
|
|
|
LG ICC One-Day International Championship - frequently asked questions
1. What is a rating?
2. What does a particular rating signify?
3. How quickly do ratings change?
4. What period does the table cover?
5. How are the results weighted?
6. Are there any 'rules of thumb' that help explain how a ranking
may change?
7. What principles are the ratings based on?
8. Why does the 'matches' column not reflect the number of actual matches that a team has played?
1. What is a rating?
A rating is worked out by dividing the points scored by the matches played, with the answer given to the nearest whole number. It can be compared with a batting average, but with points instead of total runs scored and matches instead of number of times dismissed.
After every ODI, the two teams each receive a certain number of points, based on a mathematical formula. Each team's new points total is then divided by its new matches total to give an updated rating. For the complete formula, click here.
With batting averages, if you are dismissed in your next innings for more than your average, your average will increase. Conversely, scoring less than your average will cause it to fall. Similarly, under the LG ICC ODI Championship method, the points awarded for a win will always be more than the rating the team had at the start of the match. Equivalently, a team losing an ODI will always score fewer points than its rating. So a win will always boost a team's rating and a defeat will harm it.
The ratings therefore give extra meaning to what might otherwise be regarded as 'dead rubbers'.
A tie between a higher and lower rated team will slightly benefit the rating of the lower rated team at the expense of the higher rated team. A tie between two similarly rated teams will leave both their ratings unchanged.
Matches abandoned with no result are always ignored.
2. What does a particular rating signify?
A team that over the period being rated wins as often as it loses while playing an average mix of strong and weak opponents will have a rating of close to 100.
A rating of 100 could also correspond to a side that wins more often than it loses but who has generally played more matches against weak teams. Similarly, if the majority of its matches are against strong teams, then a rating of 100 could be achieved despite having more defeats than victories.
In every match the total rating points available equals the sum of the initial rating of the two teams, so ratings can be thought of as being redistributed rather than created. There is therefore no 'inflation' in this rating system, so a rating of 120 suggests the same degree of superiority over opponents now as in the past or future, and a team can meaningfully compare its rating movements over time.
3. How quickly do ratings change?
The amount by which a rating improves after winning an ODI will depend on the rating of the opponent. A win over a much stronger team (i.e. one with a much higher rating) boosts the rating more than beating a much weaker opponent. Conversely, losing to a much stronger team will not cause the rating to drop too far, but losing to a weaker side would.
4. What period does the table cover?
The table reflects all ODIs played since August two years ago. All ODIs played until the start of next August will be added to this table, so by then the ratings will be based on three years of results. Then, next August, the first year of results will be dropped and so on.
This pattern is repeated each August, with the oldest of the three years of results removed to be gradually replaced with results of matches played over the following 12 months. Thus once a year, the rankings will change overnight without any new ODIs being played.
This process, called updating the data, will take place at the start of August each year. This time has been chosen since it is usually a relatively quiet time in the ODI calendar. The exact date of the next update will be confirmed by the ICC.
5. How are the results weighted?
All matches included within the LG ICC ODI ratings will always fall into one of three time periods.
- Period One covers the first year of matches
- Period Two covers the second year of matches
- Period Three covers the remaining more recent matches
Weightings are applied to these three groups of matches so that the ratings more fully reflect recent form. The weightings are as follows:
- Period One matches have a weighting of one third
- Period Two matches have a weighting of two thirds
- Period Three matches have a weighting of one
In the current table, matches played since last August receive a weighting of one. After next August, the weighting of matches being played now will fall to two thirds, then from the August after they will have a weighting of just one third. Finally in the August after that, they will drop out of the ratings altogether.
The number of matches played and the number of points earned in each period is multiplied by the weighting factor. For example, when the table was launched Sri Lanka had played 33 ODIs in Period One, but with a weighting of one third, this counted as 11 matches towards their rating. Similarly, their 21 ODIs in Period Two counted as 14. So the number of matches shown for Sri Lanka in the table is 11 plus 14 plus the 10 played at that time in Period Three - a total of 35. (A small technical adjustment ensures that, for all teams, the total number of matches and rating points is always a whole number.)
6. Are there any 'rules of thumb' that give me an idea how
a ranking may change?
Yes, there are a few general rules that may be useful when speculating how a team's rating could change. Note that the effect would be greater if a team has played fewer matches.
If a team is shown in the table as having played between 30-40 matches then the following would apply:
a) If playing a similarly rated team, a win would typically increase the rating by one to two points, while losing would cost one to two rating points.
b) If playing a side rated say 20-30 points higher, a win would increase the rating by around two points, but a defeat should only cost one rating point.
c) If playing a side rated say 20-30 points lower, then the opposite of b) applies - a win might be worth only one point, but a defeat might cost two points.
Finally, it might need two or three wins against a team rated 40 or more points lower to increase the rating by one point, but just one defeat might cost three points
7. What principles are the ratings based on?
The LG ICC ODI Championship table is based on the following seven principles:
i) It is based on individual matches, not on series of matches. While the result of an ODI series will remain important for the competing countries, the ratings treat each match as an entirely separate event. Therefore every ODI will count (apart from No Results) and there is no need for a stipulated minimum series length.
ii) All ODIs are treated equally. Although the ICC Cricket World Cup final will have more at stake than any other match, every ODI is subject to the same formula for ratings purposes.
iii) No account is taken of venue. Whether a side wins an ODI at home, away or at a neutral venue will not affect the ratings.
iv) No account is taken of margin of victory. The rating system records only whether a team has won, drawn or tied each match.
v) More recent results have a greater impact than older matches. To ensure the ratings fairly reflect current form, the weighting given to a particular match reduces as times passes.
vi) The method allows for the different strength of opponents played by different countries. While each team plays each other on a regular basis, a full programme of matches will not take place within the timeframes necessary for a rating system. It is therefore inevitable that some countries will have an "easier" set of ODI fixtures than others and that the method should compensate for this.
vii) The method should be as transparent as possible given the inevitable complexity of any such system. This means that the formula generating the ratings is publicly available. The ratings can be updated by anyone who chooses to apply the published formula. This also means it is possible to work out the effect future results would have on the ratings.
8. Why does the 'matches' column not reflect the number of actual matches that a team has played?
Matches are weighted so that older matches carry less significance that more recent matches. It means that the 'matches' column on the table does not reflect the actual number of matches a side has played but rather a 'matches co-efficient' that takes into account the lower weighting of older matches.
|
