Year	Percent
1971	1.055
1972	1.971
1973	2.563
1974	0.4567
1975	1.075
1976	1.106
1977	1.426
1978	4.227
1979	3.357
1980	3.109
1981	7.578
1982	4.669
1983	4.272
1984	4.418
1985	4.463
1986	4.566
1987	2.77
1988	2.679
1989	3.636
1990	2.869
1991	2.175
1992	2.399
1993	3.467
1994	2.503
1995	2.093
1996	2.996
1997	2.837
1998	3.37
1999	3.506
2000	3.045
2001	3.567
2002	4.299
2003	4.02
2004	6.656
2005	2.219
2006	3.698
2007	3.368