Year	mmol per litre
1980	6.193
1981	6.163
1982	6.133
1983	6.101
1984	6.069
1985	6.036
1986	6.002
1987	5.968
1988	5.93
1989	5.893
1990	5.852
1991	5.81
1992	5.769
1993	5.727
1994	5.69
1995	5.654
1996	5.62
1997	5.586
1998	5.555
1999	5.527
2000	5.5
2001	5.475
2002	5.452
2003	5.433
2004	5.415
2005	5.399
2006	5.388
2007	5.376
2008	5.365