Year	mmol per litre
1980	4.838
1981	4.84
1982	4.84
1983	4.84
1984	4.835
1985	4.829
1986	4.817
1987	4.804
1988	4.794
1989	4.783
1990	4.775
1991	4.77
1992	4.765
1993	4.762
1994	4.762
1995	4.762
1996	4.762
1997	4.762
1998	4.76
1999	4.753
2000	4.744
2001	4.732
2002	4.717
2003	4.702
2004	4.69
2005	4.679
2006	4.67
2007	4.666
2008	4.661