Year	mmol per litre
1980	5.269
1981	5.253
1982	5.235
1983	5.217
1984	5.201
1985	5.18
1986	5.162
1987	5.142
1988	5.12
1989	5.095
1990	5.067
1991	5.033
1992	4.995
1993	4.958
1994	4.914
1995	4.87
1996	4.827
1997	4.782
1998	4.744
1999	4.715
2000	4.693
2001	4.675
2002	4.662
2003	4.654
2004	4.651
2005	4.649
2006	4.646
2007	4.641
2008	4.636