Year,Spring_kg_tow
1968,5.609
1969,0.055
1970,2.2
1971,3.145
1972,1.542
1973,6.746
1974,0.656
1975,0.242
1976,0.254
1977,0.081
1978,0.345
1979,0.089
1980,0.202
1981,2.47
1982,0.854
1983,0.135
1984,2.611
1985,2.232
1986,1.264
1987,7.492
1988,4.133
1989,1.1
1990,1.548
1991,5.604
1992,4.705
1993,5.583
1994,5.987
1995,5.1
1996,11.101
1997,2.494
1998,3.378
1999,7.109
2000,6.934
2001,15.726
2002,7.65
2003,11.082
2004,8.088
2005,4.276