Year,Spring_kg_tow,Fall_kg_tow
1963,,12.8
1964,,13.6
1965,,9.1
1966,,4.0
1967,,7.6
1968,2.8,10.5
1969,11.2,9.3
1970,5.3,5.0
1971,4.6,6.4
1972,6.5,6.3
1973,2.9,6.6
1974,2.7,3.7
1975,1.7,2.4
1976,2.3,1.5
1977,1.0,2.8
1978,0.7,2.4
1979,1.2,1.5
1980,4.5,6.7
1981,2.0,2.6
1982,2.5,2.3
1983,2.6,2.1
1984,1.6,0.6
1985,1.0,0.7
1986,0.8,0.8
1987,0.3,0.5
1988,0.6,0.2
1989,0.7,1.0
1990,0.7,0.7
1991,0.6,0.7
1992,1.6,0.6
1993,0.5,0.5
1994,0.7,0.9
1995,2.6,0.4
1996,2.9,1.3
1997,4.4,3.8
1998,2.3,4.3
1999,9.3,8.0
2000,6.7,5.8
2001,5.0,11.6
2002,9.6,3.8
2003,6.7,4.0
2004,1.9,5.1
2005,3.4,2.5
2006,2.4,