Year	Percent
1968	16.23006
1969	15.02513
1970	16.60551
1971	15.79333
1972	18.99233
1973	13.54167
1974	8.18607
1975	7.84037
1976	8.18234
1977	8.50773
1978	7.84523
1979	5.47854
1980	4.70429
1981	8.4208
1982	10.29989
1983	11.20038
1984	13.34557
1985	14.39068
1986	14.83552
1987	14.3108
1988	14.58558
1989	16.3961
1990	8.24886
1991	15.61567
1992	19.87057
1993	15.50271
1994	20.1121
1995	20.58514
1996	18.59708
1997	8.4566
1998	10.90971
1999	7.2035
2000	4.63475
2001	6.93096
2002	8.56267
2003	8.40561
2004	6.93856
2005	6.88686
2006	5.82603
2007	4.9295
2008	3.84778
2009	5.22993
2010	5.16228
2011	4.56377
2012	4.12427
2013	4.76844
2014	4.92941
2015	4.19187
2016	3.97719
2017	2.97673
2018	2.81582
2019	3.77001
2020	6.08867
2021	3.31078
2022	2.85143