Year	mmol per litre
1980	4.713
1981	4.709
1982	4.704
1983	4.699
1984	4.694
1985	4.691
1986	4.688
1987	4.686
1988	4.684
1989	4.678
1990	4.672
1991	4.668
1992	4.664
1993	4.658
1994	4.652
1995	4.646
1996	4.639
1997	4.632
1998	4.624
1999	4.616
2000	4.608
2001	4.6
2002	4.592
2003	4.584
2004	4.576
2005	4.568
2006	4.563
2007	4.556
2008	4.55