Year	National currency (Units)
1980	0.021
1981	0.02
1982	0.02
1983	0.018
1984	0.018
1985	0.018
1986	0.019
1987	0.019
1988	0.02
1989	0.017
1990	0.017
1991	0.018
1992	0.019
1993	0.019
1994	0.018
1995	0.018
1996	0.018
1997	0.018
1998	0.018
1999	0.017
2000	0.017
2001	0.017
2002	0.015
2003	0.014
2004	0.016
2005	0.018
2006	0.019
2007	0.02
2008	0.021
2009	0.02
2010	0.02
2011	0.02
2012	0.021
2013	0.021
2014	0.02
2015	0.018
2016	0.015
2017	0.013