Year	mmol per litre
1980	4.883
1981	4.88
1982	4.877
1983	4.874
1984	4.866
1985	4.864
1986	4.859
1987	4.85
1988	4.842
1989	4.834
1990	4.823
1991	4.802
1992	4.766
1993	4.73
1994	4.695
1995	4.662
1996	4.629
1997	4.599
1998	4.57
1999	4.543
2000	4.516
2001	4.489
2002	4.47
2003	4.443
2004	4.42
2005	4.403
2006	4.392
2007	4.384
2008	4.378