Wednesday, 18 January 2017

Poor FA Cup crowds erode home advantage

I was struck by the poor attendances at some of the FA Cup 3rd round matches this month. 17,632 turned up to watch Sunderland vs Burnley, less than half Sunderland’s average home gate this season. It was a similar story at Cardiff vs Fulham, Norwich vs Southampton and Hull City vs Swansea, all of which saw crowds below 50% of their league average this season.

An interesting statistic was recently posted on Twitter by Omar Chaudhuri, of 21st Club (@OmarChaudhuri). If you take all 181 FA Cup ties that involved two EPL teams (ignoring replays and matches at neutral venue) since the 2000/01 season, you find that the home team won 46% of the matches and the away team 30%. However, if you look at the equivalent league match between the teams in the same season, you find that the home team won 52% of the matches and the away team 22%. Although the sample size is small, the implication is that home advantage is less important in cup matches.

Lower FA Cup crowds and diminished home advantage - are the two connected? This seems a reasonable hypothesis, but I’ve never seen it demonstrated explicitly. I aim to do so in this post.

Cup Matches vs League Matches

To answer the question I’ll look specifically at cup ties that involved teams from the same division, from League 2 to the EPL, and compare the outcomes to the equivalent matches in the league. This approach isolates the influence of any changes in circumstance between the two games – including lower or higher attendance.

I identified every FA Cup tie, from the third round onwards, that involved two teams from the same-division since 2000/01[1], along with the corresponding league match.  I then removed all matches at a neutral venue[2]. This left me with a sample of 357 cup matches, and the same number in the league.

I then measured what I’ll refer to as the home team’s attendance ratio -- their average home-tie FA cup attendance divided by their average home league attendance -- in each of the last 16 seasons. Season-averaged attendance statistics for both league and FA cup games (3rd round onwards) for every team were taken from Ideally, you would directly compare the attendance of each FA Cup tie with that of the equivalent league game. However, I don’t have the data for individual games, so instead I used each team’s season averages for cup and league as a proxy (but if anyone has this data and is willing to share it, please let me know!)

I used the attendance ratio to divide my sample of matches into three sub-samples: well-attended matches, mediocre attendance and poorly-attended matches. The former are defined as cup matches in which the crowd size was greater than 90% of the home team’s league average. A mediocre attendance is defined as a crowd size less than 90% but greater than 70% of their league average, and a poorly-attended one as less than 70% their league average. For each group, we’ll look at differences in the fraction of home wins, away wins and draws between the FA Cup ties and league matches.

Table 1 summarizes the results. Let’s look at the first three lines - these give outcomes for cup ties in which the attendance was at least 90% of the league average. There have been 148 such matches in the last 16 seasons: the home team won 56%, the away team 23% and 21% were draws. In the corresponding league matches, the home team won 51%, the away team 24%, and it was a draw in 26%. So, there was a small increase in the proportion of home wins relative to the league outcomes, with correspondingly fewer draws. In about a third of these ties the attendance was greater than their league average: the home side may have benefited from a more vociferous support.

Table 1

The next set of lines in Table 1 show the results for the FA Cup matches that had a mediocre attendance – those in which the attendance ratio was between 70% and 90% of the home side league average. The home team won 44% of these matches, which is slightly below the home win rate in the corresponding league matches. There is again a fall in the number of draws, but this time the away team benefits, winning 6% more often than in the league matches. The differences are small, but there is some evidence that the away team were benefitting from the below-average attendance.

However, the increase in away wins becomes much more striking when we look at poorly-attended cup matches: those in which the attendance was less than 70% of the home team's league average. The home team won only 34% of these ties, 14% below the corresponding league fixtures. The away win percentage increases to 42% and is 19% above the league outcome. Indeed, the away team has won poorly-attended cup matches more frequently than the home team. This is despite the home team winning roughly twice as often as the away team in the corresponding league fixtures (48% to 23%). The implication is very clear: when the fans don’t show up for an FA Cup tie, the team is more likely to lose. I don’t think I’ve seen any direct evidence for this before[3].

In all three sub-samples, it's worth noting that draws are down 5% relative to the corresponding league outcomes (although the beneficiary depends on the attendance). Presumably this is down to the nature of a cup tie: teams are willing to risk pushing for a win in order to avoid having to play a troublesome replay (or a penalty shoot-out during a replay).

So why are some fans not showing up? One obvious explanation is that they are simply unwilling to shell out more money beyond the cost of a season ticket. Maybe clubs should lower their prices for FA Cup matches; I’d be curious to know if any do. There could even be an element of self-fulfilling prophecy: the fans believe that their team have no real chance of winning the cup and so choose not to attend, to the detriment of their team. Perhaps the fans are aware that the cup is simply not a priority – their club may be involved in a relegation battle, for example – and that they are likely to field a weakened team.

The bottom line seems clear enough, though: if clubs want to improve their chances of progressing in the FA Cup they should ensure that they fill their stadium.

Thanks to David Shaw, Jim Ebdon and Omar Chaudhuri for comments.

[1] Data was only available for all-Championship ties from 02/03, 08/09 for L1 and 09/10 for L2.
[2] Replays were retained, although the outcome of penalty kicks was ignored (i.e., a draw at the end of extra-time was scored as a draw). There are 64 replays in the sample in total, of which 8 went to penalties.
[3] One caveat is that the sample size is pretty small: this analysis could do with being repeated on a larger sample of games (and with the specific match attendances, rather than season averages). However, the increase in the away percentage in the smallest sample (attendance ratio < 0.7) is still highly significant. 

Tuesday, 10 January 2017

The Frequency of Winning Streaks

Thirteen – an unlucky number for some. So it proved for Chelsea: just one win shy of equaling Arsenal’s record, their thirteen-match winning streak was finally ended by an in-form Spurs side. While there may be some temporary disappointment amongst Chelsea fans at having failed to set a new record, their winning run has almost certainly propelled them into the Champions League next season and made them clear favourites for the title.

Sir Alex Ferguson would often refer to momentum as being instrumental to success. A winning streak can sweep teams to the title or snatch survival from the jaws of relegation. What constitutes a good streak is clearly dependent on the team, though.  Manchester United are currently on a five-match winning run: such form would certainly be outstanding for a relegation-threatened team, but is it common for a Champions League contender? This question is itself part of a broader one: what is form and how should we measure it?

In this blog I’m going to take a look at some of the statistics of winning streaks, investigating the characteristic length of winning runs in the EPL and how it varies for teams from the top to the bottom of the table.

How well do teams streak?

I started by taking every completed EPL season since 2000/01 and dividing the teams into bins based on their points total at the end of each season (0-40 points, 40-50, 50-60, and so on)[1]. For each bin, I measured the proportion of the teams in that bin that completed a winning streak, varying the length of the streaks from 2 to 10 matches.  For example, of the 54 sides that have finished on between 50 and 60 points since the 2000/01 season, 17 (31%) completed a winning run of at least 4 matches.  Runs were only measured within a single season – they do not bridge successive seasons[2]. The results are summarized in Table 1.

Table 1: The proportion of teams that complete winning runs of two games or longer in the EPL. Teams are divided into bins based on their final points total in a season, from 0-40 points (top row) to >80 points (bottom row).

The top row gives the results for teams that finished on less than 40 points. The columns show the percentage that managed a winning streak, with the length of the streaks increasing from 2 (left column) to >10 matches (right). Three quarters of the teams in this points bin put together a winning streak of at least two games. However, the proportion drops very rapidly for longer runs: only 14% completed a 3-match winning streak and only 7% a 4-match streak. The only team to complete a 5-match winning streak was Newcastle early in 2014/15 (and this was half of the total number of games they won that season).

As you'd expect, the percentage of teams that achieve a winning streak of a given length increases as you move to higher points bins. Every team that has finished with 60 points or more has completed a 3-match winning stream. However, fewer than a quarter of those that finished with less than 70 points completed a 5-match winning streak. In general, the proportion of teams that achieve a winning streak drops off very rapidly as the length of the streak is increased. 

The exception is the title-challenging teams (the bottom row in Table 1): the percentage in this bin falls away more slowly as the the length of the winning streak is increased. 27 of the 29 teams that finished with at least 80 points put together a 5-match winning streak, 13 completed an 8-match streak and 5 completed a 10-match winning streak. This is the success-generating momentum that Ferguson habitually referred to.

In his final 13 seasons (from 2000/01 to 2012/13), Man United put together 14 winning streaks lasting 6 matches or more; in the same period Arsenal managed only 5. United won 7 titles to Arsenal’s 2. For both teams, the majority of these streaks occurred in title-winning seasons. The same applies to Chelsea and, more recently, Man City. Only two title-winning teams have failed to complete a 5-match winning streak: Man United in 2010/11 and Chelsea in 2014/15. The median length of winning streak for the champions is between 7 and 8 games.

Leicester’s 4-match winning streak at the end of the 2013/14 season saved them from relegation. It was also an unusually long run for a team finishing on around 40 points - only four other teams have managed it. Was this a harbinger of things to come? A year later, during their title-winning season, their 5-match winning streak in March/April pushed them over the line.

The implications for form

Only the best teams put together extended winning runs: 40% of EPL teams fail to put together a three-game winning streak and 64% fail to win 4 consecutive games. Perhaps momentum - and the belief and confidence it affords - is only really relevant to the top teams? Does the fixture list throw too many obstacles in the path of the smaller teams? Every 3 or 4 games a smaller team will play one of the top-5 sides, a game that they are likely to lose. This may make it more difficult for them to build up a head of steam.

On the other hand, perhaps smaller teams are able to shrug-off their defeats away to Arsenal or Liverpool and continue as before. In that case, should we discard games against the ‘big teams’ when attempting to measure their form? And to what extent do draws interrupt, or in some cases boost, a team's momentum? These are all questions that I intend to return to in future blogs.

Unbeaten Runs

Finally, I’ll leave you with the equivalent table for unbeaten runs. While the typical length of unbeaten runs in each bins is about twice as long as winning runs, most of the conclusions above still apply.

Table 2: The proportion of teams that complete an unbeaten run of length 2 or longer in the EPL. Teams are divided into bins based on their final points total in a season, from less than 40 points (top row) to more than 80 (bottom).


Thanks to David Shaw for comments.

[1] The total number of teams across all bins was 320: 16 seasons with 20 teams per season.
[2] Note that the runs are inclusive - if a team achieves a 3-match streak it will also have achieved a 2-match streak.