Year	mmol per litre
1980	4.687
1981	4.684
1982	4.681
1983	4.68
1984	4.679
1985	4.678
1986	4.676
1987	4.67
1988	4.666
1989	4.662
1990	4.657
1991	4.651
1992	4.644
1993	4.637
1994	4.63
1995	4.623
1996	4.616
1997	4.611
1998	4.606
1999	4.603
2000	4.598
2001	4.591
2002	4.584
2003	4.58
2004	4.575
2005	4.569
2006	4.565
2007	4.564
2008	4.563