Year	mmol per litre
1980	4.648
1981	4.645
1982	4.64
1983	4.628
1984	4.619
1985	4.608
1986	4.597
1987	4.587
1988	4.575
1989	4.567
1990	4.56
1991	4.555
1992	4.554
1993	4.555
1994	4.555
1995	4.554
1996	4.553
1997	4.55
1998	4.545
1999	4.539
2000	4.526
2001	4.508
2002	4.49
2003	4.474
2004	4.463
2005	4.454
2006	4.45
2007	4.448
2008	4.449