Year	Kg per Square Metre
1980	23.66
1981	23.73
1982	23.8
1983	23.87
1984	23.94
1985	24.02
1986	24.11
1987	24.21
1988	24.32
1989	24.43
1990	24.55
1991	24.67
1992	24.79
1993	24.92
1994	25.03
1995	25.15
1996	25.27
1997	25.4
1998	25.52
1999	25.62
2000	25.74
2001	25.82
2002	25.92
2003	26.03
2004	26.15
2005	26.29
2006	26.42
2007	26.56
2008	26.7