Year	mmol per litre
1980	4.912
1981	4.907
1982	4.898
1983	4.886
1984	4.875
1985	4.866
1986	4.863
1987	4.86
1988	4.855
1989	4.853
1990	4.85
1991	4.849
1992	4.851
1993	4.854
1994	4.861
1995	4.872
1996	4.88
1997	4.887
1998	4.893
1999	4.897
2000	4.9
2001	4.9
2002	4.899
2003	4.895
2004	4.892
2005	4.887
2006	4.881
2007	4.878
2008	4.874