Year	Percent
1971	34.33375
1972	34.75698
1973	27.58892
1974	16.768
1975	13.43999
1976	18.4502
1977	31.6951
1978	16.96758
1979	24.56988
1980	15.9062
1981	8.14172
1982	7.36687
1983	11.20167
1984	11.80086
1985	9.96627
1986	9.6554
1987	5.09021
1988	5.10278
1989	5.37633
1990	3.3467
1991	1.94725
1992	1.15319
1993	6.14139
1994	8.25531
1995	5.25726
1996	11.3877
1997	12.54587
1998	11.47407
1999	12.12964
2000	14.60361
2001	19.37651
2002	17.51912
2003	22.06687
2004	21.97006
2005	27.73472
2006	36.15842
2007	44.51082
2008	37.58736
2009	45.02736
2010	48.83667
2011	41.9685
2012	48.02383
2013	47.69344
2014	46.62079
2015	38.1928
2016	34.04505