Year	mmol per litre
1980	5.652
1981	5.628
1982	5.603
1983	5.579
1984	5.554
1985	5.528
1986	5.504
1987	5.485
1988	5.469
1989	5.459
1990	5.45
1991	5.442
1992	5.429
1993	5.401
1994	5.371
1995	5.334
1996	5.298
1997	5.263
1998	5.239
1999	5.225
2000	5.203
2001	5.186
2002	5.181
2003	5.178
2004	5.181
2005	5.179
2006	5.177
2007	5.169
2008	5.159