Year	Kg per Square Metre
1980	23.04
1981	23.13
1982	23.23
1983	23.33
1984	23.45
1985	23.57
1986	23.68
1987	23.79
1988	23.91
1989	24.03
1990	24.14
1991	24.27
1992	24.39
1993	24.52
1994	24.65
1995	24.78
1996	24.91
1997	25.03
1998	25.15
1999	25.26
2000	25.37
2001	25.48
2002	25.59
2003	25.69
2004	25.79
2005	25.9
2006	26
2007	26.12
2008	26.24