Year	mmol per litre
1980	5.969
1981	5.946
1982	5.922
1983	5.899
1984	5.877
1985	5.855
1986	5.832
1987	5.808
1988	5.782
1989	5.757
1990	5.731
1991	5.703
1992	5.673
1993	5.642
1994	5.609
1995	5.576
1996	5.541
1997	5.505
1998	5.471
1999	5.436
2000	5.404
2001	5.376
2002	5.349
2003	5.326
2004	5.303
2005	5.285
2006	5.269
2007	5.255
2008	5.243