For each commodity, there has also been major variations both Proportion of sales coming from Asia in the level and degree of change in C2C between individual companies. For example, the spread in C2C (using standard 50-60%in 2013 deviation as a measure) for coal decreased from 24 days to 17 days between 2007 and 2011, and then increased to 25 days between 2011 and 2013. For iron ore, the spread decreased from 32 days to 28 days, before rising to 39 days. In contrast, for copper, the spread dropped from 29 days to 25 days, and then to 21 days. C2C for the mining sector, 2013 Iron ore, coal Aluminium 30-40%in 2007 25 A number of factors can explain these WC trends overall and for days 37 each commodity group: days Increased proportion of sales coming from Asian economies: 9ka_faÕ[Yfl^Y[lgjafÖm]f[af_l`]k][lgjÌk;*;gn]jlae]`Yk been the dramatic increase in the proportion of sales coming from days Asian economies. This shift has had a positive impact on overall 39 DSO, as payment terms in some of these Asian economies, such (average) as China, are generally shorter than those in the US and Europe. Gold Copper Change in pricing practices for supply contracts: The proportion of commodities negotiated on a spot basis instead of being sold on contract has increased in recent years, contributing to lower DSO. This is particularly the case for iron ore. 48 Increased exposure to commodity trading: A number of mining 51 companies have set up trading arms in recent years, adopting days days some of the strategies used by the big commodity trading houses to make money by exploiting different prices for products in different parts of the world. This increased exposure to trading which generally carries short trade terms has also contributed to lower DSO. 5 Cash in the ground: working capital management in the mining sector