Year	mmol per litre
1980	4.782
1981	4.765
1982	4.749
1983	4.729
1984	4.71
1985	4.702
1986	4.69
1987	4.685
1988	4.675
1989	4.669
1990	4.661
1991	4.652
1992	4.647
1993	4.643
1994	4.632
1995	4.622
1996	4.615
1997	4.605
1998	4.598
1999	4.595
2000	4.598
2001	4.608
2002	4.618
2003	4.631
2004	4.643
2005	4.658
2006	4.672
2007	4.683
2008	4.694