Year	mmol per litre
1980	5.913
1981	5.893
1982	5.869
1983	5.844
1984	5.823
1985	5.802
1986	5.78
1987	5.755
1988	5.732
1989	5.707
1990	5.685
1991	5.665
1992	5.639
1993	5.62
1994	5.597
1995	5.582
1996	5.565
1997	5.549
1998	5.537
1999	5.523
2000	5.509
2001	5.495
2002	5.478
2003	5.454
2004	5.431
2005	5.411
2006	5.39
2007	5.367
2008	5.347