Year	mmol per litre
1980	6.123
1981	6.113
1982	6.1
1983	6.086
1984	6.073
1985	6.064
1986	6.055
1987	6.043
1988	6.025
1989	6.006
1990	5.987
1991	5.964
1992	5.938
1993	5.912
1994	5.887
1995	5.864
1996	5.84
1997	5.821
1998	5.805
1999	5.791
2000	5.779
2001	5.766
2002	5.759
2003	5.749
2004	5.738
2005	5.724
2006	5.71
2007	5.694
2008	5.677