Tuesday, August 30, 2011

Charts of the Day: Shots and Goals in the Top 5 European Leagues

With lots of transfers happening across borders these days, it's hard to know exactly how the leagues compare. Numbers can help with that sort of thing, but they have their limits. We know that some leagues are better than others, and we know that leagues differ in other ways like parity as well. Tactical styles differ, too, and so does the demographic composition of leagues. All of these are things that analysts have tried to measure and compare across leagues.

So far, so good. What's perhaps easy to overlook when we're searching for differences between La Liga and the Bundesliga, for example, is that teams in the top leagues of football are actually quite similar in some of the basic outputs they produce. Perhaps the most basic and easily comparably outputs are shots and goals produced (and allowed, of course). Take a look at some of the basic numbers from last season, starting with shots and followed by goals.

As it turns out, teams in the top five European leagues (Bundesliga, La Liga, Ligue 1, Premiership, and Serie A) produced similar numbers of shots and goals last year. Sure, they're not completely identical, but the range is fairly narrow - last season, supporters in Italy on average saw their teams produce the most shots at 13.7, while Ligue 1 saw the fewest at 12.4. So the range in shots teams produce is roughly between 12 and 14, and 1.5 shots per team and match on average across the five leagues.

Similar but not quite the same when it comes to goals. In 2010/11 teams produced between 1.16 (Ligue 1) and 1.44 (Bundesliga) goals per match. As I've noted before, the three leagues in the middle of the distribution (La Liga, Premier League, and Serie A) appear more similar to one another when it comes to goal production, while the other two appear slightly different (with the Bundesliga seeing slightly more and Ligue 1 slightly fewer goals).
So what about another common offensive performance statistic - the ratio of goals to shots, which historically has been right around .111 or 1 goal per 9 shots?  The leagues cluster around that mark - but Ligue 1 shooters are clearly less efficient. They need to take slightly more attempts to eventually score (roughly 1 in 9.5 shots go in). Compare this to the Premier League at the high end where 1 in 8.25 shots find the net. 
The upshot: sure, we can find differences across leagues if we look for them (and Ligue 1 really does seem to be different in that it's low-shooting, low-scoring, and less efficient in converting shots to goals), but it's also easy to forget that the production of football at the top level has some basic and shared statistical properties. Enjoy the season, whichever league you follow.

Thursday, August 25, 2011

The Decade's Best and Worst Offensive Teams in Europe's Top Leagues

Continuing on the theme of "a picture's worth a thousand words", here are the best and worst performing offensive sides from across the Top 5 European leagues (Premier League, La Liga, Bundesliga, Serie A, and Ligue 1) over the last decade (since the 2001/02 season).

The bars show the average number of goals scored per match; the axes on the two graphs have identical scales so that you can see how much better the very best teams were than the very worst. To put the graphs in perspective, these calculations include all clubs that played in one of the leagues for at least one season; and clubs can appear more than once if they qualified as one of the 10 best or 10 worst teams in multiple seasons.

So here are, first, the Top 10 sides in terms of scoring goals (average number of goals per match) since 2001/02. The winner is Barcelona's 08/09 team, which narrowly edged Chelsea's phenomenal 09/10 side. Noticeable, too, is the fact that Barcelona has three teams in the Top 10, followed by Real Madrid and Werder Bremen, each of which show up twice. Another interesting factoid: Only three leagues appear in the Top 10, with five La Liga teams (from Barcelona and Real Madrid), four from the Bundesliga (Bayern, Wolfsburg, and Bremen), and one Premier League team (Chelsea). Across the years, these teams make it into the Top 10 because they managed to score well over two goals per match. In other words, not a single Serie A or Ligue 1 side made it into the Top 10.

What about the Bottom 10 across the European leagues over the past ten years?

Tuesday, August 23, 2011

Graph of the Day: A Decade of Offensive Production in the Premier League

Just for kicks, here's a slightly different way of looking at clubs' offensive production over the course of a decade. The graph below shows average goals scored per match and season for all clubs that played in the Premier League since the 2001/02 season. 

A few things of note:
  • Only a few clubs consistently stand out; among them: Arsenal, Chelsea, Liverpool, Manchester United
  • A few clubs are consistent also-rans: Aston Villa, Everton, Tottenham
  • Clubs on the rise: Everton, Manchester City, Tottenham
  • Clubs on the decline: Blackburn, Newcastle
  • Clubs that consistently perform well but not spectacularly: Bolton, Everton, Fulham
To me, the graph also demonstrates nicely what a great achievement it is to be a consistently high performing club. To me, this puts Arsenal's record under Wenger into perspective, despite all the grief he is suffering these days. With the exception of one unusual season, Chelsea's offensive record is the same now as it was ten years ago (pre-Abramovich).

The moral: All teams go through troughs and peaks - even the very best ones. Staying at or near the top is a real feat.

Thursday, August 18, 2011

The Connection Between League Balance, Goals, and Talent

When FC Twente played Benfica Lisbon to a 2-2 draw on Tuesday night, Tottenham manager Harry Redknapp was in the stands to witness it. Mind you, 'Arry wasn't just out for a fun night of European football in Enschede - he was there to take a personal look at Bryan Ruiz, Twente's Costa Rican striker and a target for Spurs in this summer's transfer window. Ruiz has done well since joining the Dutch team, and clearly is a very talented and multidimensional player who's worth a look and has attracted serious enough attention for Redknapp to make the trek to the Netherlands.

The story of Redknapp and Ruiz is not an exception, though. As Thomas Boeschoten from catenaccio.nl points out in a recent article, English and Italian clubs have been spending the most money during the current transfer window. And while English clubs have been losing the most money from transfers, Dutch clubs have been making the biggest profits from the sales of players. In numbers, English clubs have spent about 365 million euros, while taking in about 195 million (not including the most recent Fabregas transfer). As Boeschoten rightly notes, the Dutch league has become essentially a minor league to the Premiership.

One interesting question for managers and scouts, of course, is how to evaluate performance in that league. As we have noted before, it is not entirely clear how best to evaluate a player's performance in leagues as different as Brazil's Serie A, Germany's 2. Bundesliga, or the Eredivisie. In part, it is difficult to compare 10 goals scored in the Netherlands with 10 goals scored elsewhere because of differences in league quality and league balance. In highly unequal leagues - and the Eredivisie is a lower quality league and also one of the more unequal ones - strikers like Luis Suarez or Bryan Ruiz may have an easier time standing out, especially against the lesser teams, and this may result in a higher fee than may be warranted.

All of this got me to thinking about the connection between offensive production and league balance. My hunch was that average scores should be higher in the more unequal leagues where we should see more blowouts and where the better teams are able to add a 3rd or 4th goal more easily than elsewhere.

Tuesday, August 16, 2011

Defensive Performance in the Top 4 European Football Leagues: A Statistical Review of the 2010/11 Season

Despite what Cesar Luis Menotti may want you to believe, football is a game of offense and defense. So as a follow up to my recent post on last season's offensive performance in the big leagues, I thought it was only fair to defenders and goalkeepers to take a look at who has been doing a great job keeping the opposition at bay. As before, I calculated averages on shots, accurate shots, and goals per match - but of course, this time around we're talking about shots and goals conceded.

So which teams dominated Europe in terms of preventing opponents from taking shots last year and which seemed to issue open invitations as soon as the referee blew the whistle? First up, the average number of shots conceded per match.

Turns out, many of the top offensive teams also came out as top defensive teams last year. Perhaps heeding Cruyff's advice that the other side can't score if they don't have the ball (I'm paraphrasing), Barca allowed the fewest number of shots on goal in all of Europe. That's an astonishing testimony to their ability to keep the ball away from the other side, and explains why they could dominate La Liga and Europe despite having defensive players that are not on par with their midfield and strikers, quality-wise. We already knew that Arsenal actually defended very well in the Premier League last year, but it is perhaps a little surprising this put them second in Europe in terms of allowing the other side to take shots.  Surprises at the high end of performance: Nuernberg and Newcastle.

But shots don't have to be accurate to count. So which teams did particularly we degrading the quality of shots taken - measured as the average number of accurate shots teams conceded in 2010/11?

Friday, August 12, 2011

Graphs of the Day: Foul Play in the Premier League in 2010/11

In anticipation of an opening weekend of great football, I thought it'd be fun to take a quick look at fouls committed in the Premier League last year. Who fouled the most and the least?* Take a look.

Spurs led the league with the smallest number of fouls called per match at 9.5; at the high end, Bolton were called for infractions an average of 12.63 times per match. That's a difference of about 30 percent. But what's also noticeable about the graph is that the range of fouls committed by PL teams is actually quite small, on the order of 10-12, and that there seems to be little connection to how teams fared in the league overall.

What this graph hides, however, is that some teams consistently foul less or more, while others commit lots of fouls on occasion but have other matches when they commit very few fouls.

Tuesday, August 9, 2011

Home Field Advantage and the Value of Away Draws in the Premier League: The 2010/11 Season

I've previously written about home field advantage in football. While there's no shortage of debate about the actual source of the home field advantage by learned and and not so learned minds alike, the facts are straightforward: home field advantage is a statistical fact. Across the big leagues of European football, more matches end with the home team winning than end with any other outcome (away win or draw). The numbers vary slightly across leagues, with around 45-48% of matches resulting in a home win and the remainder roughly evenly split between wins for the away team and draws.

The statistical fact of the home field advantage suggests that one key to a successful season is to capitalize on home field advantage and to neutralize another team's potential home field advantage as much as possible when playing away. A quick look at match data for the 2010/11 season allows us to get a handle on which teams have enjoyed the most and least amount of home field advantage and which have been best able to neutralize it.

Before we look at the numbers for individual teams, here's first the overall proportion of home and away wins in the Premier League for last season. Home teams won 47% of the time; away teams won 24% of the time; and the remainder ended in draws. Clearly, last season was no exception to the general rule that the home team wins about as often as it does not, and winning about twice as often as the away team.

But we can assume that not all teams were equally adept at turning home field advantage into wins. As it turns out, there was huge variation across clubs in the league when it came to taking advantage of home field advantage.

Friday, August 5, 2011

Shots and Goals In the Big 4: Offensive Performance Across Leagues in 2010/11

During the past year, I have compared teams across the Big 4 leagues (Bundesliga, Premier League, La Liga, Serie A) with regard to various performance indicators. With the Bundesliga about to get underway tonight, I thought it'd be interesting to see where they all ended up by the end of the season, and to find out what we may expect for next year. So for today, here are season totals (averages per team and match) on three dimensions of offensive production - shots, shots on target, and goals - across the four leagues and 78 teams in total.

On average, teams across the four leagues took about 13 shots per match (12.96). Real Madrid led the top European leagues at almost 19 (18.9), followed by Inter, Dortmund, Chelsea, and Palermo. At the bottom end, we saw 3 English clubs, with Blackburn, Wolves, and Birmingham who were bottom in Europe at a measly 8.6 shots per match. That's a whopping 54% fewer shots than Madrid. But this did not necessarily imply an overall inferiority of English clubs, it turns out, as teams from all four leagues are distributed across the graph. Perhaps somewhat surprisingly, Barcelona came in only at number 8 overall in average shots per match, with roughly the same season production as Milan and Arsenal. What is perhaps most surprising about the graph is the relatively narrow range that the vast majority of teams find themselves in when all is said and done. With the exception of a few truly unusual teams at both the high and low end of the distribution, a large percentage of them are located somewhere between (roughly) 12 and 14 shots per game. And interestingly, some amazing teams are neighbors with some very mediocre ones. So one thing to take away from this first graph is that there is relatively little that separated the great from the not so great when only the average number of shots per season is considered.

Wednesday, August 3, 2011

Premier League Defensive Bulwarks in 2010/11: Arsenal (?!) and Manchester United

In the next installment of "what happened last season in the Premier League?", here are season totals on teams' defensive prowess.  Much has been made of Arsenal's inability to defend well and its need to improve defense during this transfer window. But the numbers tell a slightly different story - at least in part. Turns out, Arsenal conceded the fewest shots overall last year and the fewest accurate shots - so in overall numbers they did best - while Manchester United defended most effectively on an accurate shot to shot basis. Where Arsenal did less well and came in 13th in the league is in the ratio of accurate shot conceded to overall shots conceded.

But first things first. As the first two graphs show, the teams that struggled also had the leakiest defenses last year in terms of total number of shots conceded. Teams that defended surprisingly well in terms of overall shots were Wigan (yes, I know, Wigan again), as well as Liverpool and Newcastle.

Most of the data for other teams should not come as a real surprise to anyone, but it's interesting to see the totals nonetheless. I'll also note a few interesting exceptions.

Tuesday, August 2, 2011

The Price of Football in England and Scotland: A BBC Survey

Here are tables for the prices of football across England's four leagues and the Scottish Premier League, courtesy of the BBC. I have yet to see if there's a correlation between price and success, but it's interesting stuff nonetheless.

Monday, August 1, 2011

Is the Premier League the League of Draws? Data From the 2010/11 Season

Over the last couple of days, I've been doing some work on my databases for the last few years' worth of league play. In the process, I've come across some interesting patterns that I thought were worth sharing. One of them was simply the distribution of full time results in the Premier League last year.

For the league as a whole, the 2010/11 season saw more draws in the Premiership than elsewhere. 29.2% of all matches EPL teams played last year ended in a draw; that's several percentage points higher than in the other three leagues I have been writing about (Bundesliga, La Liga, and Serie A). Here's a graph of match outcomes at the level of teams (with wins and losses equal by definition).

To stats aficionados who know more than I do this may be old hat, but I thought this was a curious pattern - curious in part because we have seen in other analyses that the Premiership has become more imbalanced over the last few years. Of course, these do not have to be inconsistent - you can still have a few dominant teams that win all of their matches and everyone else producing mostly draws. At the same time, a more imbalanced league producing more draws is interesting (well, to me).

So which teams were particularly likely to produce draws last year? That is, who was most responsible for the high % of draws in the Premier League last season?