Year	mmol per litre
1980	5.974
1981	5.948
1982	5.923
1983	5.898
1984	5.877
1985	5.859
1986	5.838
1987	5.812
1988	5.786
1989	5.761
1990	5.732
1991	5.712
1992	5.688
1993	5.667
1994	5.647
1995	5.627
1996	5.609
1997	5.592
1998	5.574
1999	5.553
2000	5.533
2001	5.516
2002	5.496
2003	5.474
2004	5.457
2005	5.439
2006	5.424
2007	5.406
2008	5.389