Year	mmol per litre
1980	6.2
1981	6.168
1982	6.136
1983	6.106
1984	6.076
1985	6.049
1986	6.022
1987	5.994
1988	5.964
1989	5.934
1990	5.904
1991	5.876
1992	5.845
1993	5.815
1994	5.784
1995	5.751
1996	5.717
1997	5.684
1998	5.658
1999	5.634
2000	5.607
2001	5.583
2002	5.559
2003	5.534
2004	5.514
2005	5.494
2006	5.479
2007	5.466
2008	5.452