Year	mmol per litre
1980	4.754
1981	4.746
1982	4.735
1983	4.72
1984	4.705
1985	4.691
1986	4.675
1987	4.662
1988	4.65
1989	4.639
1990	4.628
1991	4.619
1992	4.613
1993	4.608
1994	4.604
1995	4.601
1996	4.6
1997	4.601
1998	4.602
1999	4.6
2000	4.598
2001	4.597
2002	4.593
2003	4.589
2004	4.585
2005	4.582
2006	4.579
2007	4.576
2008	4.574