Year	mmol per litre
1980	4.745
1981	4.734
1982	4.73
1983	4.726
1984	4.721
1985	4.713
1986	4.706
1987	4.698
1988	4.685
1989	4.674
1990	4.672
1991	4.672
1992	4.67
1993	4.667
1994	4.666
1995	4.663
1996	4.654
1997	4.646
1998	4.637
1999	4.626
2000	4.611
2001	4.599
2002	4.583
2003	4.565
2004	4.554
2005	4.54
2006	4.53
2007	4.52
2008	4.51