Year	current US$
2000	0
2001	0
2002	0
2003	0
2004	0
2005	0
2006	1
2007	1
2008	1
2009	1
2010	1
2011	1
2012	2
2013	2
2014	2
2015	3
2016	2
2017	3
2018	2
2019	2