Premier League Points Efficiency

It would be tautological to say that you win in football by scoring more goals than your opponent. What is interesting is that scoring more goals and letting in fewer works across games in a season as well, as data from the English Premier League shows.

We had seen an inkling of this last year, when I had showed that points in the Premier League were highly correlated with goal difference (96% R square for those that are interested). A little past the midway point of the current season and the correlation holds – 96% again.

In other words, a team’s goal difference (number of goals scored minus goals let in) can explain 96% of the variance in the number of points gained by the team in the season so far. The point of this post is to focus on the rest.

In the above image, the blue line is the line of best fit (or regression line). This line predicts the number of points scored by a team given their goal difference. Teams located above this line have been more efficient or lucky – they have got more points than their goal different would suggest. Teams below this line have been less efficient or unlucky – their goal difference has been distributed badly across games, leading to fewer points than the team should have got.

Manchester City seem to be extremely unlucky this season, in that they have scored about five fewer points than what their goal difference suggests. The other teams close to the top of the league are all above the line – showing they’ve been more efficient in the way their goals have been distributed (Spurs and Arsenal have been luckier than ManYoo, Chelski and Liverpool).

At the other end of the table, Huddersfield Town have been unlucky – their goal difference suggests they should have had four more points – a big difference for a relegation threatened team. Southampton, Newcastle and Crystal Palace are also in the same boat.

Finally, the use of goal difference is used to break ties in league tables is an attempt to undo the luck (or lack of it) that would have resulted in teams under- or over-performing in terms of points given the number of goals they’ve scored and let in. Some teams would have gotten much more (or less) points than deserved by sheer dint of their goals having been distributed better across matches (big losses and narrow wins). The use of goal difference is a small attempt to set that right.

Money can buy me Premier League performance

The following graph plots the premier league performance (in terms of points) for the 2012-13 season as a function of the team’s wage bill. Apart from a few outliers here and there the correlation is astounding:

wageperformance

 

The red line is the line of best fit (according to a linear regression) and comparing team standings with respect to the line shows how well teams performed relative to what their wages would predict.

It is interesting to see that Manchester City almost fall off the charts in terms of wages, yet they could not translate this to on-pitch performance. It can also be seen that Manchester United, Spurs and Everton significantly over-performed given their wage bills.

Based on the wage bill, it would have also been reasonably easy to predict that Wigan Athletic and Reading would get relegated at the end of the season – though it must be mentioned they underperformed their wage bills, but QPR should have done a lot better given the size of their pay packet.

A simple linear regression of points against wage bill shows that every GBP 4 million increase in the wage bill leads to one additional point in the premier league! And the regression has an R-square of 69% – which means that the team’s wage bill can predict 69% of the variation in the team’s performance! Which is extremely significant.

The screenshot of the regression is given below: wagerank

 

Note that in this post we only use the wage bill and not any transfer fees paid. However, the assumption is that the two are reasonably correlated and we are not losing out on any information by using only the wage bill.

 

 

Premier League Sub-Tables

Ahead of the Chelsea-Liverpool game on Sunday, the pre-match show showed a “sub-table” of the premier league of how the top 8 teams had fared against each other. While by definition, the Premier League is played among 20 teams, and your result against Chelsea is as important as that against Crystal Palace, looking at sub-leagues like this one can help us gauge what the overall points table is trying to hide.

In this post I’ll just show the sub-league of the top of the league (top 3 to top 7) and bottom of the league (bottom 3 to bottom 7). Offered without further comment.

topbottom7

Premier League – Home and Away

So we are halfway through what is easily the most competitive English Premier League in recent times. To illustrate, Liverpool were on top of the table at Christmas, and after two successive defeats, lie fifth at the New Year. Anything can happen this season and the top seven or eight teams are all still in contention.

One interesting factor this season, however, has been the fixture list. For example, only Manchester United among the top eight has played at Anfield (Liverpool’s home ground) this season. Liverpool has played every other top eight team away so far – which means they will face them all at home in the second half of the season.

On the other hand, Manchester City has hosted all top eight teams bar Chelsea so far! Which means they will be playing all these teams away this season! Sunderland is currently bottom. However, they have hosted mostly top-half teams (which are significantly superior to them) and played away to other bottom half teams which are of comparable strength.

The following table illustrates who has hosted whom. The table is to be read row-wise. “H” and a red cell means that the team in the corresponding row has hosted the team in the corresponding column. A while cell and “A” implies otherwise.Notice that this is the only point of time in the season when we can do this analysis for now everyone has played everyone else exactly once. Teams in this table are ordered in descending order of points.

plhomeaway

 

 

 

Can we have a metric of who has had the best set of home fixtures this season so far? For this, let us define a “home index”. For each team, this is calculated as the difference between the average points of the teams played at home and the average points of the teams played away.

Let me illustrate. Arsenal, for example have so far hosted Chelsea, Everton, Liverpool, Spurs, Southampton, Hull, Stoke, Villa and Norwich. These teams have an average of 28.6 points as of now. Arsenal has so far visited the rest of the clubs, viz. Manchester City, Manchester United, Newcastle, Swansea, Cardiff, West Brom, Crystal Palace, Fulham, West Ham and Sunderland. These teams average 22.6 points as of now. So Arsenal’s home index is 28.6 – 22.6 = 6.0

A positive home index implies a team has played more strong teams at home and weak teams away. It is not easy to say, however, whether this implies an easier second half of the season. Arsenal, for example, would be happy to host the weaker teams they have traveled to, but the fixture list means they will be traveling to more strong teams, which means the potential for dropping points is higher.

Among the relegation-threatened teams, Sunderland has the highest “home index”, and for them the season is likely to become better – in the second half, they will get to host the weaker teams whom they can reasonably expect to beat while traveling to stronger teams (who they’ve lost to anyway) won’t change much. Thus, a high home index is a positive for lower-ranked clubs.

The following graph shows the home-away index for all clubs:

haindexNotice that both Arsenal and Manchester City have had an easier run so far – hosting the better teams. it will be interesting to see how they perform in the second half of the season when they travel to the better clubs. Especially given that Liverpool and Chelsea have had a bad run of fixtures in the first half and are likely to improve in the second half.

Finally, the first part of the post assumes that teams are better off playing at home rather than away. Is this really true? To check this, let us look at the average points scored by teams in home and away games. This number should be taken with a pinch of salt, though – teams with a high home index are less likely to perform significantly better at home compared to away.

Based on the performance so far, the average points in home games is 0.28 more than the average points in an away game. However, we also need to take into account the home index. When we regress the difference between home and away points against the home index, we find that for every one point higher in home index, the difference between home and away performance comes down by 0.04 (the R-square, for those that are interested in such things, is 15%).

The following table shows the difference in home and away performances of different teams:

homeaway2Most teams, you can see from this table, have done better home than away. The significant exceptions are Aston Villa, Manchester United and Spurs. Villa and Manchester United have a high Home Index which possibly explains this. There is no explanation of spurs’ home form, though.

 

 

 

 

 

Analyzing Premier League Performance so far

After yet another round of matches this weekend, Liverpool were unable to beat a 10-man Newcastle, and have slipped to third spot, with Chelsea going ahead of them on goal difference. Arsenal thumped Norwich to go clear at the top of the table. Manchester United continued to flounder, drawing at home to Southampton, who are the most improved team this season, compared to the last.

Now, the problem is that each team has a different fixture list. Some teams (such as Manchester United) have had an insanely tough set of fixtures so far this season. Others such as Arsenal have had it quite easy (the eight games Arsenal have played this season have all been fixtures that they won last year!). How do we account for this relative ease in fixtures to see how well teams have been performing?

In chess, one of the popular tie breaker methods used for “Swiss League” tournaments is called the “Solkoff method”. According to this method, the tie breaker score for each player is the sum of points scored by all his opponents. In a swiss league, each player plays against a different set of players, so a higher Solkoff score means a player has played his games against tougher opponents, and has hence done better than someone else with the same points tally but who has played weaker opponents. The question is if we can use these principles to evaluate football teams at this point in the season.

I propose what I call the “Modified Solkoff” score. Here, we not only take into account the total points of each opponent of a team, but also the result of the game against the particular opponent. This is then normalized by the total points scored by all your opponents. Take Arsenal for example. Their opponents so far this season have a total of 69 points as of today. Of the eight games they’ve played, Arsenal have lost to Aston Villa and drawn at West Brom. So the numerator of Arsenal’s Modified Solkoff score becomes 0 * Aston Villa’s points (10) + 1 * West Brom’s points (10) + 3 * total points of all their other opponents, which  amounts to 157. This is then normalized by the total  points tally of their opponents so far (69) and we get Arsenal’s normalized Modified Solkoff score of 2.28. You can see that the maximum possible Solkoff score is 3 (if a team has won all its games) and the minimum is 0 (losing all games). The higher the Solkoff score the better (better performance against better opponents).

This is what the Modified Solkoff table looks like as of today (21st October 2013). Arsenal may not have played the toughest opponents but the fact that they have won so many of their games means that they are on top. They are interestingly followed by Manchester City and then Southampton. Manchester United is buried somewhere in the bottom half of the table:

 

It is also interesting to note that Sunderland is ahead of Crystal Palace at the bottom of their table. This is due to the fact that Palace’s only points so far have come against Sunderland, while Sunderland earned their point from a draw with high-flying Southampton.

This also shows that Liverpool’s early season highs have come on the back of wins against relatively weaker teams (it doesn’t help their cause that Manchester United is classified as a “weak team” thanks to their performance so far), and thus their early season table topping is unlikely to sustain.

Let me know in the comments what you think of this method of computing a normalized score based on a team’s opponents so far.

PS: This table will be regularly updated (after each “matchday”), so if you are reading this after October, some of the notes may not match what is there in the table.

Advertising liqour

I miss liquor advertisements. I really do. There might be some noble intention in preventing liquor companies from advertising openly through television and print (many of them have resorted to surrogate ads, though), but the quality of liquor advertising that I remember from the late 90s (when I was too young to drink) was pretty good. Many of those ads were quite cult.

I remember the vodka ad (forget the brand) where the guy looks through his glass and sees other people in the bar turning into ferocious creatures (the best being the guy with a big moustache turning into a walrus). Then there was the “be what you wanna be” Bacardi ad –  I loved the jingle. The “swinging to Bacardi blast” just doesn’t have the same effect as “sipping on Bacardi rum”. Then there was the Haywards ad, of the two men playing darts in the bar. Such #kvltness! They should have a way to show adult rated ads on TV during late nights, etc. and permit liquor advertising then.

Last night, though, I came across a very interesting form of liquor advertising. Liquor companies are allowed to advertise at point of sales, so you see these huge liquor ads that usually sponsor the boards of “wine shops”. Similarly, you see beer and cocktail glasses that would have been branded with certain brands (in London, for example, the bartenders would be very particular about serving drinks in the right brand of glass. Carlsberg (which I drank a lot of that summer thanks to newfound Premier League loyalty) would be served in a Carlsberg glass only. Guinness in a Guinness glass only. Indian bartenders usually don’t care about this and are happy to give you kingfisher in a Beck’s glass). And in some American style bars, you see neon-light boards advertising certain brands.

At the Hard Rock Cafe, however, where I was last evening, Eristoff vodka has figured out a nice (and innovative – for me at least since I haven’t seen this form elsewhere) way of advertising. They advertise on the menu! It is very simple. Every vodka-based cocktail, or cocktail containing vodka that is there on the menu, says “Eristoff vodka” rather than just “vodka”. For example, the description under “screwdriver” would read “Eristoff Vodka with orange juice”. Simple and elegant way of creating brand awareness, and recall value. And well-targeted also, since if you order the cocktail you immediately get to ‘taste’ the vodka.

There is a reason I avoid whisky-based cocktails. A couple of times I’ve had them, they’ve been generally infused with cheap local molasses-based whisky which has given me  a bad hangover. Now, if only some better whisky company can start branding the menu of whisky-based cocktails, there is a good chance that people like me might order and drink more of whisky-based stuff. Though it still remains that I prefer my whisky neat.