Year	mmol per litre
1980	4.993
1981	4.982
1982	4.965
1983	4.947
1984	4.93
1985	4.916
1986	4.903
1987	4.89
1988	4.88
1989	4.869
1990	4.863
1991	4.859
1992	4.859
1993	4.861
1994	4.864
1995	4.865
1996	4.868
1997	4.87
1998	4.873
1999	4.878
2000	4.882
2001	4.883
2002	4.885
2003	4.886
2004	4.888
2005	4.889
2006	4.892
2007	4.897
2008	4.901