Year	mmol per litre
1980	4.935
1981	4.93
1982	4.92
1983	4.909
1984	4.894
1985	4.876
1986	4.856
1987	4.838
1988	4.823
1989	4.809
1990	4.798
1991	4.787
1992	4.777
1993	4.771
1994	4.768
1995	4.766
1996	4.765
1997	4.763
1998	4.762
1999	4.759
2000	4.755
2001	4.751
2002	4.746
2003	4.741
2004	4.736
2005	4.732
2006	4.727
2007	4.719
2008	4.712