Year	mmol per litre
1980	5.434
1981	5.427
1982	5.419
1983	5.409
1984	5.401
1985	5.39
1986	5.381
1987	5.372
1988	5.361
1989	5.35
1990	5.338
1991	5.316
1992	5.29
1993	5.259
1994	5.23
1995	5.207
1996	5.184
1997	5.166
1998	5.147
1999	5.129
2000	5.116
2001	5.104
2002	5.094
2003	5.083
2004	5.073
2005	5.061
2006	5.048
2007	5.039
2008	5.028