Year	mmol per litre
1980	5.661
1981	5.65
1982	5.636
1983	5.622
1984	5.6
1985	5.582
1986	5.56
1987	5.537
1988	5.52
1989	5.5
1990	5.476
1991	5.451
1992	5.425
1993	5.404
1994	5.382
1995	5.352
1996	5.331
1997	5.318
1998	5.305
1999	5.294
2000	5.284
2001	5.276
2002	5.271
2003	5.264
2004	5.259
2005	5.258
2006	5.26
2007	5.265
2008	5.268