Men’s Soccer NPI Dials
Dials have been set for men’s soccer as follows:
• Winning percentage / strength of schedule: 25/75
• Home/away win/loss weights: 1.1/0.9
• Quality win bonus threshold: 53.5
• Quality win bonus multiplier: 0.6
• Overtime weight: 100/0
• Minimum retained wins: 10
This page will give a short overview of what each one means. For details of how the NPI is calculated, see here; the quick version is that each match is given a value based on outcome and opponent strength, and the NPI is a weighted average of those values.
Similar to the RPI, winning percentage makes up approximately 25% of a team’s NPI, and the remnant is strength of schedule. However, the way SOS is calculated in the NPI results in it having a narrower range than the old version of SOS. The result is that winning percentage has a greater influence on NPI than it did on RPI.
The first number refers to the weight of a home loss or road win, the second to a road loss or home win. In effect that means that in a road match, a win counts as 1.1 wins and a loss counts as 0.9 losses. A road tie counts as 0.55 wins and 0.45 losses, since the NPI treats a tie as half a win and half a loss (this also means that ties are eligible for QWB and win/loss exclusion). All neutral-site results are weighted at 1.0.
When a team beats an opponent whose NPI is above 53.5, a bonus is applied to that match, equal to (opponent’s NPI minus 53.5) times 0.6. But since this bonus is applied to the value of a single match, which is just one of many matches included in the weighted average, it will usually take several such wins to have a meaningful effect on the team’s NPI. Note that the bonus is not static, but will change over the course of the season along with that opponent’s NPI.
All this means is that overtime wins count exactly the same as regulation wins.
NPI always excludes losses that would raise a team’s overall NPI. With wins that would lower NPI, it’s more complicated; once a team has 10 wins (as weighted for home/away), their wins over the weakest opponents are removed from the calculation until one of two things happens (a) they’re left with only 10 wins, or (b) all the remaining wins raise their NPI. Timing of these wins is irrelevant to the calculation; the most damaging wins are removed first, regardless of when they occurred. And as with the QWB, it’s entirely possible for it to change, over the course of the season, which wins are damaging enough (or losses good enough) to be excluded.