[14] Other income statement disclosures

The cost of materials rose by €117.7 million in the reporting year to €3,691.4 million (2017: €3,573.7 million).

Personnel expenses went up by €110.5 million to €2,100.2 million in 2018 (2017: €1,989.7 million). These personnel expenses included wages and salaries of €1,653.4 million (2017: €1,567.8 million), social security contributions of €364.2 million (2017: €343.5 million) and expenses for pensions of €82.6 million (2017: €78.5 million). The interest cost from the unwinding of the discount on estimated pension obligations is not recognised under personnel expenses and is instead reported under financial expenses as a component of interest cost of the defined benefit obligation. Pension expenses essentially comprised the pension entitlements of €41.4 million vested in 2018 (2017: €40.6 million) and unrecognised past service cost of €1.4 million (2017: income of €0.1 million) arising from plan amendments and curtailments.

Impairment losses and depreciation expenses on property, plant and equipment together with impairment losses and amortisation expenses on intangible assets amounted to €897.9 million in the reporting year (2017: €896.6 million). Inventories were written down by €25.3 million (2017: €18.0 million).