Year	mmol per litre
1980	6.032
1981	5.992
1982	5.952
1983	5.915
1984	5.882
1985	5.852
1986	5.825
1987	5.798
1988	5.772
1989	5.746
1990	5.715
1991	5.681
1992	5.646
1993	5.609
1994	5.576
1995	5.544
1996	5.509
1997	5.474
1998	5.442
1999	5.409
2000	5.378
2001	5.347
2002	5.318
2003	5.291
2004	5.264
2005	5.239
2006	5.211
2007	5.182
2008	5.154