Year	mmol per litre
1980	6.179
1981	6.144
1982	6.109
1983	6.078
1984	6.047
1985	6.019
1986	5.992
1987	5.965
1988	5.941
1989	5.922
1990	5.899
1991	5.876
1992	5.852
1993	5.827
1994	5.802
1995	5.778
1996	5.754
1997	5.732
1998	5.712
1999	5.691
2000	5.672
2001	5.654
2002	5.637
2003	5.624
2004	5.609
2005	5.594
2006	5.582
2007	5.57
2008	5.557