Year	mmol per litre
1980	4.99
1981	4.974
1982	4.956
1983	4.94
1984	4.924
1985	4.908
1986	4.891
1987	4.871
1988	4.85
1989	4.824
1990	4.793
1991	4.755
1992	4.701
1993	4.64
1994	4.575
1995	4.51
1996	4.442
1997	4.379
1998	4.328
1999	4.283
2000	4.248
2001	4.224
2002	4.206
2003	4.193
2004	4.185
2005	4.181
2006	4.177
2007	4.173
2008	4.169