Year	mmol per litre
1980	4.812
1981	4.811
1982	4.808
1983	4.803
1984	4.803
1985	4.8
1986	4.801
1987	4.802
1988	4.8
1989	4.797
1990	4.796
1991	4.793
1992	4.792
1993	4.794
1994	4.792
1995	4.791
1996	4.789
1997	4.79
1998	4.789
1999	4.785
2000	4.775
2001	4.76
2002	4.741
2003	4.73
2004	4.722
2005	4.71
2006	4.702
2007	4.694
2008	4.686