Year	Kg per Square Metre
1980	26.25
1981	26.36
1982	26.46
1983	26.56
1984	26.65
1985	26.72
1986	26.8
1987	26.88
1988	26.95
1989	27.03
1990	27.09
1991	27.04
1992	27.03
1993	27.05
1994	27.09
1995	27.11
1996	27.19
1997	27.25
1998	27.36
1999	27.51
2000	27.64
2001	27.8
2002	27.93
2003	28.01
2004	28.08
2005	28.15
2006	28.23
2007	28.32
2008	28.41