Year	mmol per litre
1980	5.827
1981	5.829
1982	5.831
1983	5.834
1984	5.837
1985	5.835
1986	5.831
1987	5.828
1988	5.821
1989	5.813
1990	5.802
1991	5.788
1992	5.761
1993	5.717
1994	5.668
1995	5.62
1996	5.565
1997	5.509
1998	5.456
1999	5.408
2000	5.365
2001	5.328
2002	5.293
2003	5.264
2004	5.244
2005	5.222
2006	5.198
2007	5.174
2008	5.148