Year	Kg per Square Metre
1980	22.93
1981	23.11
1982	23.29
1983	23.49
1984	23.71
1985	23.92
1986	24.12
1987	24.31
1988	24.48
1989	24.66
1990	24.86
1991	25.05
1992	25.23
1993	25.43
1994	25.63
1995	25.83
1996	26.02
1997	26.23
1998	26.45
1999	26.65
2000	26.86
2001	27.05
2002	27.24
2003	27.43
2004	27.63
2005	27.83
2006	28.04
2007	28.25
2008	28.46