In this piece I want to consider whether seasonality affects the number of goals scored and whether we can use this information to bet more intelligently on football matches.
Historically, the issue of seasonality in goal scoring rates has always been a factor to consider for bettors.
Typically we could expect more goals to be produced when pitches are in top condition and players are at peak fitness.
Alongside these two conditions, the importance of individual matches can also influence the number of goals scored. For example, it is a fair assumption to make that there are fewer goals scored in matches involving two title contenders or a pair of relegation candidates. It is also fair to suggest that more goals are scored in meaningless fixtures towards the end of the season, especially in matches between teams with little or nothing to play for.
Because pitch conditions are now considerably better season-round in the main European leagues, I looked into the number of goals scored in each month across the four “major” leagues (English Premier League, German Bundesliga 1, Italian Serie A and Spanish Primera Division) to see if the theory of seasonality still holds.
Although I have simply considered the number of goals scored in each calendar month, there are a number of different ways to test for seasonality. We can analyse the number of goals scored in each individual round of fixtures, in every four rounds, or even split the football season between the international breaks that are held at fairly consistent times of the year.
Each of the graphs below shows the average percentage of goals scored in each month compared to the total number of goals scored for that period. So, if there was an average of 2.8 goals scored in November over a ten-year period and the combined average number of goals over ten years was 2.8, the figure for November would be 100%.
I have also added in “Final Round” averages, which are the results from the last set of fixtures in a league season and traditionally see more goals scored:
The main takeaway from the graphs is that goal scoring rates begin at lower than average levels in August, before increasing around October as each squad presumably hits peak match fitness. There is then a dip during the business end of the season around February/March when there are more meaningful “must-win” matches being played.
Bundesliga 1 is the only league here that has a complete winter break and we can see from the graph that the scoring rate takes longer to return to average, almost replicating the phase at the very start of the season.
What is common across all four leagues is the vast increase in goals scored at the end of each season, especially in the final round of each league.
This can be explained by the amount of meaningless games that occur at this time, with titles won, relegations suffered and European places often sealed before the final set of fixtures take place. This then gives each team more freedom to play more relaxed football, which can breed creativity, cause mistakes and ultimately lead to more goals.
Germany, Spain and Italy’s top divisions all show an almost identical pattern over both the five- and ten-year time periods, though there is a small difference in the numbers for England’s Premier League during the middle months of the season.
To a degree this can be explained by the increase in average goals scored in the past five seasons compared to the last ten.
The ten-year average for this league is 2.66 goals, but the smaller sample of five years has a much higher average of 2.75. So far this season, the number of goals is back down to 2.64 and it may be the case that we are going through a low goals period in this league, having enjoyed a boom between 2009/10 and 2013/14.
In 2015/16 to date, Bundesliga 1 and Serie A have both followed their five and ten year period pattern well, indicating a normal season in these leagues.
However, there has been some difference in the Primera Division, where the goals in August were exceptionally lower than average, and in the Premier League, where we saw a higher number of goals in September but a significantly lower number in December.
In drawing conclusions from the data, it is fair to suggest that seasonality does still exist in the four major European leagues and I think this pattern will also hold for most other leagues around the world. Although we may see some anomalies, it remains my firm view that seasonality should always be considered when betting on football matches.