Year	Kg per Square Metre
1980	24.4
1981	24.53
1982	24.66
1983	24.79
1984	24.92
1985	25.07
1986	25.21
1987	25.35
1988	25.49
1989	25.63
1990	25.77
1991	25.92
1992	26.07
1993	26.22
1994	26.38
1995	26.53
1996	26.67
1997	26.81
1998	26.94
1999	27.06
2000	27.18
2001	27.3
2002	27.43
2003	27.55
2004	27.66
2005	27.77
2006	27.89
2007	27.99
2008	28.1