Year	mmol per litre
1980	4.847
1981	4.827
1982	4.807
1983	4.786
1984	4.763
1985	4.736
1986	4.708
1987	4.683
1988	4.658
1989	4.635
1990	4.61
1991	4.589
1992	4.574
1993	4.561
1994	4.552
1995	4.546
1996	4.545
1997	4.547
1998	4.554
1999	4.562
2000	4.575
2001	4.587
2002	4.599
2003	4.607
2004	4.616
2005	4.629
2006	4.645
2007	4.662
2008	4.679