# Country Value in 2012 Value in 2018 1 Chile 21,962 15,546 2 Russia 2,528 4,476 3 Japan 4,542 4,125 4 DR Congo 2,350 3,629 5 Zambia 2,349 3,060 6 Kazakhstan 3,637 2,802 7 Australia 2,904 2,377 8 Congo 331 2,046 9 China 703 1,867 10 Peru 1,989 1,846