Year	mmol per litre
1980	5.366
1981	5.359
1982	5.349
1983	5.341
1984	5.333
1985	5.324
1986	5.315
1987	5.305
1988	5.297
1989	5.288
1990	5.28
1991	5.268
1992	5.249
1993	5.21
1994	5.178
1995	5.155
1996	5.141
1997	5.129
1998	5.118
1999	5.106
2000	5.097
2001	5.085
2002	5.076
2003	5.064
2004	5.05
2005	5.036
2006	5.023
2007	5.011
2008	5