Year	mmol per litre
1980	5.887
1981	5.865
1982	5.842
1983	5.817
1984	5.795
1985	5.772
1986	5.748
1987	5.722
1988	5.696
1989	5.668
1990	5.644
1991	5.62
1992	5.593
1993	5.572
1994	5.546
1995	5.527
1996	5.505
1997	5.483
1998	5.465
1999	5.446
2000	5.427
2001	5.409
2002	5.389
2003	5.365
2004	5.343
2005	5.325
2006	5.308
2007	5.291
2008	5.276