Newcastle did as bad as Leicester City did well. And Southampton’s season was as impressive as Leicester’s. Two statements I’m sure you don’t agree with. But both are true (according to data).
How good is your knowledge of the Premier League? Answers to follow.
Combining data analysis with sport isn’t a shiny new concept. From Billy Beane and the Oakland A’s to Mark Warburton’s sacking from Brentford FC, data analysis is now prominent in sport worldwide. But with this season alone seeing Leicester City spending £217.95 million less than Manchester City on transfer fees and player wages, and picking up 15 more points, it had me wondering; maybe the data scientists are starting to have a larger impact?
Can you buy the title?
Managers and scouts regularly scour databases hoping to unearth the next Riyad Mahrez. It is impossible to measure the impact that data analysis has had on the performance of Premiership teams, but the use of data in player recruitment can be investigated.
The visualisation below compares the final Premier League table with the club spending (wages + net transfers) on players this season.
In 04/05, Chelsea bought the title. In 11/12, Manchester City bought the title. The more you spend on players, the greater chance you have of winning the title. Likewise, the less you spend, the more likely you are to be relegated. All bold statements, but widely agreed with.
Clearly, Leicester massively exceeded all our expectations this year, but I wasn’t expecting the two tables to be so dissimilar. Newcastle really had a shocker and Swansea deserve a lot of credit for staying up, considering they ranked bottom for squad investment.
Are this season’s figures an anomaly?
I have collected data relating to the amount spent on players for each Premier League team since the inception of the competition in 1992. Money spent on players has changed over time. In 1992 title winners Manchester United spent a mere £2.3 million, while Aston Villa finished bottom this year spending £52.5 million. Using the inflation rate to compare spending across seasons is inappropriate as football transfer fees don’t follow normal economic trends.
The graph below shows British transfer records since the inception of the Premier League.
Clearly just looking at the rise in transfer fees is interesting, but it doesn’t tell us very much. To explore the impact of this further, I have calculated the ratio of team spending against average team spending that season.
For example, in 2000-2001 Premier League teams together spent £635 million on transfers and wages. This gives an average of £31.75 million per club. Manchester United spent £41.7 million that season, which is 1.31 times the average.
The graph below plots the final points total of each team in Premier League history against this ratio. The average spend per team is shown by the vertical dotted black line.
So it turns out the more you spend compared to other teams the more likely you are to win. Who would have guessed it?
On average, relegated teams spend 0.58 that of the average team in the league and the Champions spend 2.16 times the average. This graph also shows the big leap between mid table teams and the top 4 – with top 4 teams, on average, spending over 2 times more than mid table teams.
How has this changed over time?
To investigate, I have now grouped the teams into 5 categories depending on their final league position for each season from 00/01 to 15/16. It shows the average spend of those teams compared to the average spend in the league that season (the horizontal dotted black line).
The ratios have been consistent over the years, with top four teams and the champions regularly spending between 1.5 and 3 times more than average. The relegated teams are often those that spend less than half the average. But, 2015-2016 was different. The average ratios of the 5 categories range between 0.5 and 1.5 times the average.
While this looks like an anomaly, and probably is, you can see that the range between the highest spenders and the lowest spenders has decreased over the last three seasons. I can speculate that this is because the so called ‘smaller’ teams are spending more and the ‘bigger’ teams are unable to spend 3 times as much as them.
Is the future bright?
Of course, there are far more factors to consider when linking player recruitment to league position, so many that I won’t entertain the idea of naming them. Football is a game of two halves; in the first half the more you spent the more likely you were to do well. However, in the second half, after the introduction of the data scientist, this correlation may be weakening and Leicester City are potentially the first of many to defy the odds. Long may it continue.
So how well do you know the Premier League? See below for proof, if you ever need it, that Leeds United are one of the six biggest clubs in England.