Year	mmol per litre
1980	5.41
1981	5.401
1982	5.386
1983	5.37
1984	5.357
1985	5.342
1986	5.327
1987	5.313
1988	5.297
1989	5.278
1990	5.259
1991	5.244
1992	5.235
1993	5.229
1994	5.225
1995	5.218
1996	5.211
1997	5.205
1998	5.201
1999	5.194
2000	5.184
2001	5.169
2002	5.144
2003	5.122
2004	5.101
2005	5.087
2006	5.078
2007	5.072
2008	5.065