Year	Kg per Square Metre
1980	20.03
1981	20.15
1982	20.27
1983	20.41
1984	20.55
1985	20.69
1986	20.86
1987	21.03
1988	21.19
1989	21.36
1990	21.54
1991	21.72
1992	21.88
1993	22.04
1994	22.19
1995	22.34
1996	22.5
1997	22.67
1998	22.85
1999	23.05
2000	23.24
2001	23.44
2002	23.63
2003	23.82
2004	24.01
2005	24.21
2006	24.41
2007	24.62
2008	24.82