We Sailors group our results together into series, short one offs are called regattas. But its the series - the longer groups of races, travelers circuits and the weekly club races.
Usually we score them the same, the ISAF rules make on change to the scoring of "Series longer than a Regatta" but this only deals with the scores for non races. This is as study and thought experiment on the systems problems.
Nice day Nasty day.
Lets take Sarah Sailor, a good sailor but not the best, one bight sunny day she gets up and joins 19 other boats in race one of a series. She comes 4th - a good score. Beats 3/4 of the fleet. The following week Sarah Sailor has to go to School Sports day, and the weather is therefore terrible. However Publik Skool Boy decides to go sailing, being an public school boy he thinks he's better than he is and so on. The hideous weather doesn't scare him, not his inability to maintain his boat. Only 3 boats enter the race in the horrible conditions, he gets lapped but god knows how makes it across the finish line. He's just sailed incredibly badly and got 3 points, where as Sarah Sailor, got 4 points for her masterful performance the previous week.
Wanna do well sail in the really bad weather days!
This is because the scores take no account of how many competitors there are in a race, this also happens to encourage turnout.
Too many discard anomalies
Primarily the scoring system is designed to line up competitors best to worst, however this is not the only consideration in the design. Other factors are applied some of these are: providing sufficient qualifiers. Encouraging turnout. etc. Ties have to be broken too.
A8.1 If there is a series-score tie between two or
more boats, each boat’s race scores shall
be listed in order of best to worst, and at the first
point(s) where there is a difference the tie shall be
broken in favour of the boat (s) with the best score(s).
No excluded scores shall be used.
Usually there is some form of "Discard" "Qualification" or "Races to Count" now officially called "Excluded Scores". These are often confused to being the same thing. All are particularity relevant to the longer series. The system as published in appendix a is pretty simple. However if you have not many races or lots of excluded scores you get a lot of ties to break and thanks to the the first rule tie break rule (A8.1) precious few to break them on quite frequently having to break them on the last race rule (A8.2)