Year	mmol per litre
1980	4.723
1981	4.731
1982	4.738
1983	4.745
1984	4.752
1985	4.761
1986	4.769
1987	4.781
1988	4.794
1989	4.811
1990	4.83
1991	4.85
1992	4.87
1993	4.893
1994	4.915
1995	4.938
1996	4.961
1997	4.98
1998	4.992
1999	5.003
2000	5.015
2001	5.026
2002	5.04
2003	5.053
2004	5.066
2005	5.078
2006	5.091
2007	5.104
2008	5.117