Year	Years
1971	3.554
1972	5.498
1973	4.038
1974	4.429
1975	4.585
1976	4.941
1977	5.393
1978	4.569
1979	4.32
1980	4.559
1981	3.713
1982	2.006
1983	2.884
1984	2.521
1985	2.922
1986	2.317
1987	2.777
1988	2.558
1989	2.315
1990	2.007
1991	2.101
1992	2.729
1993	2.383
1994	2.655
1995	2.018
1996	2.614
1997	2.516
1998	2.733
1999	3.225
2000	3.154
2001	3.273
2002	3.036
2003	3.247
2004	3.316