Tldr: Comparing recent performances shows, that currently PL is the strongest by far. But only since around 3-4 years.
How to compare Leagues?
The easiest way to compare leagues is to use results based metrics like EUFA coefficient, where the Premier league is clearly leading. A drawback of the UEFA coefficient is, that it only covers teams playing in UEFA competitions and the point distribution is kind of arbitrary (like guaranteed points for entry to the CL group stage), that UEFA games are often skewed towards top teams due to seeding (historically successful teams play easier opposition in the group compared to upstarts) and that you get the same number of points for winning games regardless of opposition.
Nevertheless, it is possible to gauge the strength of teams purely based on the results. You just need a lot of them. The very useful website “clubelo.com” is using the ELO system which is also used in chess as well in order to compare the strengths of European teams using UEFA and domestic games.
What is ELO?
Clubelo.com: “The Elo system works with only a single number, the Elo value. The difference in Elo points between two teams directly translates to a likelyhood of winning against that team. When a club with a 20% winning probability (and 80% losing probability, draw counting as half win/ half loss) wins it will gain 4 times more Elo points than when it loses so that the two clubs Elo values will remain stable relative to each other if the club actually wins 20% of the games. Should the club win more than 20%, their Elo values will converge accordingly.”
The advantage of the ELO system is, that it can be applied to all games played. While UEFA games redistribute points between the top teams playing in the tournaments, domestic games redistribute points within the league according the domestic results. This means we gain in a proxy for comparing teams that don’t play internationally.
So what is the relative strengths of the Premier League?
In the figure below the current ELO rating for all first tier teams of the English, Spanish, French, German and Italian League are shown.
So what can we see here? Each symbol represents the ELO of a team. The teams are ordered according their strengths. So we can compare the team’s strengths across leagues, by comparing the symbols vertically. What we can see from this for instance, is City slightly edging Bayern, more significantly Real and Napoli and shitting on PSG. In general, we can see that all PL teams are stronger than the respective teams from the other leagues. We can also compare horizontally. What we can see from this, is for instance that the 11th best team from the PL (WestHam) is better than the 8th best Buli & SeriaA Team, the 6th best PD team and the 4th best L1 team. Lastly, we can also see that the ELO system has some issues with capturing rapidly changing form/ strength of a team. Hence United is still trailing Barca somewhat and even Liverpool (which are still rated 2nd best in the PL, bohoo).
So how has the relative strength of the Premier league evolved over time?
What is nice, is that clubelo.com also offers a look into historical data. So we can check the situation in the past, for instance in March 5th 2016 (which coincidentally is the starting date of the thread). The ELO is shown below.
What we can observe here is a fully reversed situation. PD teams were clearly dominating. So much, that the 5th best team from Spain (Villareal) was ranked slightly above the PL’s best (City).
So since when is the Premier League the best?
It depends on the metric. If we take the average ELO of all teams in the league, then the Premier League overtook PD in Spring 2019, see below. We can also see, that at the time the thread was started PL wasn’t even clearly 2nd best. We can also take from the chart below, that the biggest lead, a league had over the others, was SA in the early 1990s followed by PD in the early 2000s followed by PD in the middle 2010 followed by PL now. The most equality between top 3 leagues was in the late 1990s and early 2010s.
So how did the situation look in Spring 2019?
Apparently PL was a total clusterfeck, with 6 teams dominating (Arsenal being the 6th best in the PL and 13th best in Europe) and the worst teams on a similar level as in France. Just look at the point gap between 6th and 7th.
But in general the PL is most competitive? What about the “big 4”? Surely the bottom teams of the league is the best in the world.
Below is the average ELO of the top 4 teams, bottom 4 teams as well as the difference between top 4 and bottom 4. Since January 2019 the PL has the strongest Top 4. Since Autumn 2020 it also has the strongest bottom 4. Regarding the difference between top and bottom (last plot), a general trend of increasing gap is visible in all leagues. This is driven by the improvement of the top teams. Currently, the PL is the second most imbalanced, only beaten by SA. In March 2016 it was much more balanced indeed, however, PD was more balanced at the time still.
