Note 11: Operating expenses

The research and development expenses are broken down as follows:


	Six months ended June 30
(thousands of euros)	2019		2018
Research and development expenses
Personnel expenses		20,419		22,051
Sub-contracting, collaborations and consultants		25,624		21,023
Depreciation and amortization		2,670		489
Small equipment and supplies		1,946		2,581
Conferences, travel expenses		792		1,234
Rental⁵		333		965
Others		454		1,604

Total research and development expenses		52,238		49,946

The sales and marketing expenses are broken down as follows:


	Six months ended June 30
(thousands of euros)	2019		2018
Sales and marketing expenses
Personnel expenses		5,961		4,147
Fees		1,541		3,869
Depreciation and amortization		391		3
Marketing, tradeshows and travel expenses		342		1,692
Others		92		17

Total sales and marketing expenses		8,327		9,728

By nature, the breakdown of general and administrative expenses is as follows:


	Six months ended June 30
(thousands of euros)	2019		2018
General and administrative expenses
Personnel expenses		15,809		11,379
Fees		5,947		5,322
Depreciation and amortization		426		323
Insurance policies		1,071		726
Corporate communication and travel expenses		422		995
Rental⁵		164		582
Others		1,986		1,808

Total general and administrative expenses		25,825		21,135

⁵	As of June 30, 2019, rentals are composed of rents related to leases ending within less than 12 months and to leases of low value assets, excluded from the scope of application of IFRS 16 standard, and of rental expenses.

Personnel expenses

As of June 30, 2019, the average headcount of the Group was 322 employees, compared with 244 employees as of June 30, 2018.

Personnel expenses are broken down as follows:


	Six months ended June 30
(thousands of euros)	2019		2018
Wages and salaries		25,332		14,256
Social security contributions		7,138		4,556
Expenses for pension commitments		1,223		1,100
Employer contribution to bonus shares		455		906
Share-based payments		8,040		16,758

Total personnel expenses		42,188		37,577