Year	mmol per litre
1980	6.007
1981	5.895
1982	5.782
1983	5.668
1984	5.554
1985	5.438
1986	5.326
1987	5.22
1988	5.121
1989	5.03
1990	4.947
1991	4.875
1992	4.811
1993	4.762
1994	4.723
1995	4.691
1996	4.669
1997	4.659
1998	4.664
1999	4.685
2000	4.725
2001	4.775
2002	4.835
2003	4.904
2004	4.979
2005	5.058
2006	5.137
2007	5.219
2008	5.3