Year	mmol per litre
1980	4.71
1981	4.706
1982	4.7
1983	4.69
1984	4.681
1985	4.671
1986	4.661
1987	4.652
1988	4.644
1989	4.64
1990	4.639
1991	4.638
1992	4.642
1993	4.647
1994	4.652
1995	4.657
1996	4.663
1997	4.668
1998	4.672
1999	4.675
2000	4.672
2001	4.666
2002	4.661
2003	4.658
2004	4.657
2005	4.658
2006	4.661
2007	4.666
2008	4.673