Year	mmol per litre
1980	6.033
1981	6.01
1982	5.984
1983	5.957
1984	5.929
1985	5.899
1986	5.873
1987	5.844
1988	5.819
1989	5.796
1990	5.769
1991	5.745
1992	5.717
1993	5.694
1994	5.672
1995	5.655
1996	5.64
1997	5.629
1998	5.621
1999	5.615
2000	5.614
2001	5.616
2002	5.618
2003	5.622
2004	5.628
2005	5.64
2006	5.65
2007	5.662
2008	5.674