8. Staff costs

Notes to the consolidated financial statements

The table below summarizes the number of our employees on 31 December 2019 and 2018:

 

2019

2018

Number of employees on 31 December

1,003

725

Total

1,003

725

The average number of employees during the years 2019 and 2018 was:

 

Year ended 31 December

 

2019

2018

Executive officers

5

5

Research and development

667

553

Corporate and support

193

119

Total

865

677

Their aggregate remuneration comprised:

 

Year ended 31 December

(thousands of €)

2019

2018

Wages and salaries

(116,408)

(61,619)

Social security costs

(16,858)

(11,003)

Retirement benefit costs

(4,715)

(2,994)

Other personnel costs

(39,109)

(27,375)

Total personnel costs

(177,090)

(102,991)

The other personnel costs mainly related to costs for warrants granted of €32.5 million (2018: €21.3 million). For the costs of warrants granted, see note 28.