Year	mmol per litre
1980	4.824
1981	4.805
1982	4.787
1983	4.775
1984	4.765
1985	4.753
1986	4.743
1987	4.732
1988	4.718
1989	4.705
1990	4.696
1991	4.69
1992	4.687
1993	4.681
1994	4.679
1995	4.677
1996	4.677
1997	4.675
1998	4.674
1999	4.669
2000	4.665
2001	4.655
2002	4.641
2003	4.63
2004	4.62
2005	4.611
2006	4.607
2007	4.607
2008	4.608