Year	mmol per litre
1980	5.951
1981	5.926
1982	5.894
1983	5.862
1984	5.831
1985	5.801
1986	5.769
1987	5.744
1988	5.721
1989	5.694
1990	5.666
1991	5.651
1992	5.638
1993	5.62
1994	5.6
1995	5.589
1996	5.578
1997	5.574
1998	5.573
1999	5.571
2000	5.565
2001	5.562
2002	5.55
2003	5.533
2004	5.519
2005	5.501
2006	5.475
2007	5.45
2008	5.426