Year	mmol per litre
1980	5.954
1981	5.929
1982	5.901
1983	5.873
1984	5.845
1985	5.821
1986	5.798
1987	5.774
1988	5.754
1989	5.731
1990	5.707
1991	5.681
1992	5.66
1993	5.638
1994	5.618
1995	5.602
1996	5.583
1997	5.563
1998	5.545
1999	5.526
2000	5.509
2001	5.494
2002	5.479
2003	5.464
2004	5.452
2005	5.443
2006	5.435
2007	5.432
2008	5.425