4.1 INVENTORIES

The detail of inventories at 31 December 2017 and 2016 is as follows:

Of the commercial inventories recognised at 31 December 2017, EUR 286 million (EUR 239 million in 2016) relate to the Real Estate business in Poland, of which EUR 128 million (EUR 100 million in 2016) relate to land and building lots and EUR 158 million (EUR 139 million in 2016) relate to property developments at different stages of completion.

EUR 126 million of raw materials and other supplies relate to the Construction Division, mainly at its subsidiaries in the US and Canada, amounting to EUR 53 million (EUR 49 million in 2016), and Budimex, amounting to EUR 54 million (EUR 32 million in 2016). In addition, at the end of 2017 EUR 17 million had been recognised in relation to the Services Division, mainly at its subsidiary Amey amounting to EUR 13 million (EUR 22 million in 2016).

Lastly, bid and mobilisation costs includes contract costs for EUR 124 million (EUR 69 million in 2016). As explained in Note 1.3.3.4, Revenue recognition, assets related to the costs of obtaining a contract (bid costs) and to the costs incurred to fulfil a contract (mobilisation costs) are recognised. As regards bid costs, the Group recognised EUR 23 million (EUR 9 million in 2016) corresponding to construction contracts.

Additionally, there are mobilisation costs amounting to EUR 101 million (EUR 60 million in 2016), of which EUR 27 million relate to service contracts and EUR 74 million to construction contracts. The change of EUR 25 million under this heading is due to the application of IFRS 15 (see Note 1.3.1.1) and corresponds to a reclassification from the Receivables heading, since certain mobilisation costs had been recognised under that heading.

Both for bid and mobilisation costs, amortisation is carried out systematically, in accordance with the transfer of goods and services to which the asset corresponds. In 2017, EUR 1 million of bid costs and EUR 31 million of mobilisation costs were amortised.