Year	mmol per litre
1980	4.845
1981	4.84
1982	4.831
1983	4.823
1984	4.807
1985	4.785
1986	4.76
1987	4.737
1988	4.717
1989	4.698
1990	4.684
1991	4.671
1992	4.659
1993	4.65
1994	4.647
1995	4.642
1996	4.639
1997	4.635
1998	4.633
1999	4.628
2000	4.621
2001	4.614
2002	4.607
2003	4.6
2004	4.594
2005	4.591
2006	4.587
2007	4.582
2008	4.577