Year	mmol per litre
1980	6.169
1981	6.133
1982	6.1
1983	6.064
1984	6.029
1985	5.992
1986	5.958
1987	5.923
1988	5.887
1989	5.852
1990	5.815
1991	5.774
1992	5.734
1993	5.694
1994	5.657
1995	5.624
1996	5.592
1997	5.561
1998	5.535
1999	5.508
2000	5.482
2001	5.459
2002	5.437
2003	5.416
2004	5.396
2005	5.379
2006	5.365
2007	5.354
2008	5.343