Year	Kg per Square Metre
1980	25.73
1981	25.87
1982	26.03
1983	26.18
1984	26.34
1985	26.49
1986	26.65
1987	26.78
1988	26.93
1989	27.07
1990	27.19
1991	27.29
1992	27.37
1993	27.45
1994	27.53
1995	27.61
1996	27.7
1997	27.81
1998	27.92
1999	28.05
2000	28.19
2001	28.33
2002	28.44
2003	28.55
2004	28.65
2005	28.77
2006	28.9
2007	29.02
2008	29.14