Year	mmol per litre
1980	4.477
1981	4.475
1982	4.469
1983	4.463
1984	4.455
1985	4.448
1986	4.44
1987	4.436
1988	4.436
1989	4.436
1990	4.438
1991	4.443
1992	4.451
1993	4.459
1994	4.471
1995	4.483
1996	4.494
1997	4.505
1998	4.515
1999	4.524
2000	4.537
2001	4.552
2002	4.568
2003	4.58
2004	4.59
2005	4.602
2006	4.612
2007	4.622
2008	4.633