Year	Kg per Square Metre
1980	25.48
1981	25.55
1982	25.63
1983	25.71
1984	25.79
1985	25.88
1986	25.97
1987	26.06
1988	26.17
1989	26.28
1990	26.4
1991	26.52
1992	26.65
1993	26.78
1994	26.93
1995	27.08
1996	27.24
1997	27.41
1998	27.59
1999	27.78
2000	27.97
2001	28.15
2002	28.33
2003	28.5
2004	28.65
2005	28.81
2006	28.95
2007	29.1
2008	29.24