Year	mmol per litre
1980	4.99
1981	5.025
1982	5.06
1983	5.092
1984	5.126
1985	5.158
1986	5.19
1987	5.216
1988	5.238
1989	5.25
1990	5.258
1991	5.267
1992	5.276
1993	5.29
1994	5.298
1995	5.301
1996	5.299
1997	5.294
1998	5.287
1999	5.276
2000	5.261
2001	5.241
2002	5.214
2003	5.185
2004	5.156
2005	5.124
2006	5.092
2007	5.061
2008	5.029