Year	current US$
2000	7.419101886484664
2001	6.598192591357537
2002	7.29584702970236
2003	8.084081176121051
2004	9.257146986781168
2005	10.585669609769406
2006	12.881311477829763
2007	15.73015571928427
2008	17.83925116757165
2009	17.330986437614076
2010	17.759209455683134
2011	17.87333746700094
2012	18.125084153830038
2013	20.167317395953035
2014	19.71114442309944
2015	19.970541089659584
2016	17.333260752931285
2017	15.882872002156553
2018	14.235424794336527
2019	14.809728767525677
2020	14.609177914986706
2021	14.92261682263707