Year	mmol per litre
1980	5.84
1981	5.789
1982	5.738
1983	5.687
1984	5.636
1985	5.581
1986	5.528
1987	5.477
1988	5.43
1989	5.386
1990	5.344
1991	5.304
1992	5.266
1993	5.233
1994	5.204
1995	5.179
1996	5.155
1997	5.136
1998	5.12
1999	5.11
2000	5.108
2001	5.107
2002	5.11
2003	5.115
2004	5.123
2005	5.133
2006	5.144
2007	5.155
2008	5.165