Year	Kg per Square Metre
1980	25.46
1981	25.51
1982	25.56
1983	25.6
1984	25.64
1985	25.69
1986	25.74
1987	25.79
1988	25.85
1989	25.91
1990	25.98
1991	26.05
1992	26.14
1993	26.21
1994	26.28
1995	26.34
1996	26.41
1997	26.49
1998	26.55
1999	26.61
2000	26.67
2001	26.73
2002	26.79
2003	26.85
2004	26.9
2005	26.96
2006	27.02
2007	27.09
2008	27.17