Year	mmol per litre
1980	4.662
1981	4.657
1982	4.654
1983	4.652
1984	4.65
1985	4.649
1986	4.646
1987	4.641
1988	4.63
1989	4.614
1990	4.596
1991	4.574
1992	4.548
1993	4.523
1994	4.496
1995	4.471
1996	4.448
1997	4.428
1998	4.412
1999	4.396
2000	4.383
2001	4.371
2002	4.36
2003	4.349
2004	4.338
2005	4.326
2006	4.314
2007	4.302
2008	4.29