Year	mmol per litre
1980	5.786
1981	5.768
1982	5.75
1983	5.732
1984	5.714
1985	5.694
1986	5.673
1987	5.656
1988	5.639
1989	5.624
1990	5.61
1991	5.596
1992	5.571
1993	5.528
1994	5.485
1995	5.444
1996	5.393
1997	5.342
1998	5.294
1999	5.253
2000	5.219
2001	5.193
2002	5.172
2003	5.159
2004	5.158
2005	5.155
2006	5.15
2007	5.145
2008	5.138