Year current US$ 1993 6.3597228437149855 1994 6.773599623210208 1995 8.779367888892631 1996 8.113009206989078 1997 10.943788694623688 1998 11.245706792748635 1999 11.717324649149425 2000 10.467332267858112 2001 9.080724157737077 2002 10.636674098415716 2003 13.349188916784362 2004 13.00784788274082 2005 13.897789287262068 2006 14.61334267942271 2007 15.903642294879836 2008 22.048692388835562 2009 20.984829224385074 2010 20.01103795313794 2011 26.637707862785778 2012 20.055118905555858 2013 24.044050910195264 2014 19.685891894381886 2015 25.418018627852057 2016 20.91868947531041 2017 17.91646074430703 2018 16.061664339215362 2019 16.61075768288112 2020 20.46004318566482 2021 17.537134198542553 2022 17.17337180673269