Foreign players are much more numerous in Europe (47.7% of squads) and in the MLS (48.5%) than in Asia (17.9%) and South America (13.6%). Great discrepancies also exist according to position. While foreign footballers account for 34.9% of forwards, they only represent 20.5% of goalkeepers. The relative presence of foreign players among defenders and midfielders is around 25%.

From an age perspective, foreign footballers in the leagues studied are on average older than nationals: 27.1 years compared to 25.7. While only 13.2% of U21 footballers are foreigners, the latter represent 33.8% of players over 28 years of age. Nevertheless, the average age of first migration tends to diminish in relationship with the international recruitment of a greater number of very young players.

In six European leagues surveyed, more than half of teams are made up of foreign players: England, Belgium, Italy, Turkey, Portugal and Germany. At the opposite end of the spectrum, foreign players account for less than 10% of squads in Brazil, Uruguay, Venezuela, Costa Rica, Colombia, Argentina, Paraguay, Uzbekistan and Iran.

The study also warns the wealthiest clubs against the risk of abandoning the training of local players in favour of their import. The Report reminds that “all the clubs having left their mark on modern football in Europe (Real Madrid, Ajax, Bayern Munich, Milan, Manchester United, Barcelona) and elsewhere (Boca Juniors, River Plate, Santos, Flamengo) had several home-grown pillars, whose presence made a major contribution to their legendary status”.

The Report concludes that “talented players are born all over the world. What is missing in the first instance, is not so much talents, as a favourable context for their development. So as to encourage clubs worldwide not to take the easy road and fall into the trap of recklessly importing players and selling their souls to the market actors, training must be better protected and better paid”.

In 34 cases out of 49, the gap between the fee invested to recruit a big-5 league player and his estimated transfer value was less than 2 million €. The strong correlation between fees paid and predicted (76%) confirms the accuracy of the algorithm created from the analysis of more than 1,500 paying fee transfers occurred since 2010.

Our study allows us highlighting the payment of much higher or, more rarely, lower transfer compensations than fees paid in the recent past for players with similar characteristics. The inflation in transfer costs compared to the 11 previous transfer windows was 28%.

According to our estimates, the most over-paid player was Jackson Martínez: 42 million € instead of 18.2 (+23.8 million €). Among the five most over-paid footballers are another player transferred to China, Ramires (+10.8 million €), as well as three footballers signed by English Premier League clubs: Lewis Grabban (+7.8 million €), Timm Klose (+7.5) and Andros Townsend (+7.0).

The most under-paid player was also transferred between Premier League clubs: Jonjo Shelvey. According to our analysis, while the transfer value of the young English national A-team midfielder was 30.9 million €, Newcastle was able to sign him for "only" 16 million € (-14.9). The transfers of Mario Suárez to Watford and Augusto Fernández to Atlético Madrid were also cheaper than expected.

The figures for all big-5 league footballers transferred for money in January is available in issue number 136 of the Big-5 Weekly Post. For more information about the CIES Football Observatory approach, please refer to Monthly Reports number 6 and number 7. A transfer value calculator for big-5 league players is also freely available online.

Previous research from the CIES Football Observatory suggests that sticking on a core group of footballers often allows clubs obtaining top level results. No team who heads the table in its respective league used more than 24 players. This figure is 20 for Napoli, 22 for Leicester and Bayern Munich, 23 for Paris St-Germain and 24 for Barcelona.

Conversely, frequent line-up changes tend to reflect anxiety which is detrimental to the improvement of results. So far, clubs at the bottom of the table in their respective league on average fielded 26.0 players. This figure is 22.2 for clubs heading the table, 23.6 for the top three ranked teams per league and 25.3 at big-5 league level.

The indicator of the grip on the game refers to the number and location of passes achieved compared to opponents, while that of dangerousness is the ratio between the number and quality of shots attempted and conceded. More information about the CIES Football Observatory collective key performance indicators is available in issues number five and number seven of the Monthly Report.

The average value between grip on the game and dangerousness results in a composite indicator which allows us measuring the level of dominance of teams and estimating in an objective way the number of points that a club should have obtained accordingly. The comparison between points estimated and achieved permits us highlighting the most and least efficient teams. Future will tell what is the part of luck for the most efficient teams and that of bad luck for the most inefficient ones.

The most efficient big-5 league club so far was Stoke City. With a dominance of 0.53, the Premier League team should have obtained 0.72 points per match, which is 0.78 less than it was actually the case. At second position in the big-5 and at the top of the Liga table is Villarreal. Their dominance was 0.89, which should have allowed them obtaining only 1.24 points per match instead of 2.0 (+0.76).

Issue number 133 of the Big-5 Weekly Post also presents the data for grip on the game, dangerousness and dominance of all teams. The latter indicator suggests that the favourite clubs for the European club competitions are Bayern Munich for the Champions League and Napoli for the Europa League. Manchester City is at the top of the English Premier League table ahead of Leicester and Arsenal.

Dominance ranking

1) Bayern Munich 4.02
2) Naples 3.06
3) Paris St-Germain 2.14
4) Manchester City 2.11
5) Dortmund 2.10
6) Barcelona 2.00
7) Fiorentina 1.89
8) Real Madrid 1.87
9) Juventus 1.68
10) Atlético Madrid 1.66
11) Leicester 1.64
12) Arsenal 1.59

The average age on the pitch recorded for England during matches played in 2015 was 25.6 years. In Europe, only the Netherlands fielded footballers as young as the English ones. The youthfulness of the players available to Roy Hodgson is the sign of a renaissance which prefigures a promising future. At the opposite end of the spectrum, Scotland fielded the most seasoned footballers: 29.0 years on average.

The analysis on height shows that the average full international is 181.9cm. Great discrepancies exist between national teams. The average height on the pitch of the country who fielded the tallest players, Serbia, was 10cm greater than that of the country who played with the shortest footballers, Chile: 185.6 compared to 175.6cm. However, the short stature of the Chileans did not stop them winning the Copa América.

With regard to clubs employing internationals of the most competitive nations, the study shows the great concentration of talent in the wealthiest leagues. Almost one minute out of two was played by big-5 league footballers. In total, 68.9% of minutes were played by footballers under contract with foreign clubs. England is the only squad who did not field footballers playing abroad.

Finally, the Report highlights that 11.3% of national A-team footballers were born outside of the association represented. Two countries heavily relied on players born abroad: Algeria and Albania. Algeria fielded 21 players born in France, while 17 foreign-born footballers played for Albania. In the global era, the disjuncture between the country of birth and that represented will probably strengthen in the years to come.

Find out the other CIES Football Observatory Monthly Reports here.

During this season, footballers with national A-team caps in 2015 played 90% of domestic league minutes at Real Madrid. This figure is above 80 % for five other big-5 league clubs, four English Premier League teams (Chelsea, Manchester City, Manchester United and Tottenham), as well as Juventus. The only big-5 league team who did not field players with national A-team caps in 2015 is the Italian side Carpi.

The average percentage of minutes by active internationals per league varies between 58% in the English Premier League and 24% in the Spanish Liga. The figures for the three remaining big-5 leagues are 40% in the German Bundesliga, 31% in the Italian Serie A and 29% in the French Ligue 1. The overall percentage at big-5 league level is 36%.

Tomorrow, the CIES Football Observatory will publish the first Monthly Report of the year 2016 focusing on the squad profile of the best performing national A-teams.