Year	mmol per litre
1980	4.534
1981	4.51
1982	4.486
1983	4.467
1984	4.447
1985	4.433
1986	4.419
1987	4.403
1988	4.39
1989	4.378
1990	4.363
1991	4.348
1992	4.332
1993	4.315
1994	4.292
1995	4.274
1996	4.255
1997	4.237
1998	4.219
1999	4.201
2000	4.183
2001	4.164
2002	4.148
2003	4.136
2004	4.131
2005	4.126
2006	4.119
2007	4.111
2008	4.1