Year	mmol per litre
1980	4.807
1981	4.799
1982	4.784
1983	4.768
1984	4.753
1985	4.74
1986	4.726
1987	4.713
1988	4.703
1989	4.69
1990	4.679
1991	4.669
1992	4.662
1993	4.662
1994	4.661
1995	4.66
1996	4.66
1997	4.66
1998	4.661
1999	4.663
2000	4.664
2001	4.662
2002	4.661
2003	4.661
2004	4.66
2005	4.656
2006	4.655
2007	4.658
2008	4.659