Year	Percent
1975	9.79916
1976	9.30483
1977	8.66122
1978	8.25343
1979	8.13165
1980	8.58068
1981	7.66281
1982	7.77048
1983	7.56618
1984	7.2428
1985	6.87784
1986	6.55735
1987	5.28088
1988	5.19531
1989	5.22057
1990	5.39694
1991	4.82514
1992	4.27803
1993	4.37299
1994	4.18627
1995	3.7971
1996	3.44915
1997	3.42307
1998	2.89938
1999	2.88616
2000	2.95364
2001	2.76433
2002	2.67231
2003	2.53577
2004	2.37972
2005	2.27826
2006	2.00119
2007	2.38037
2008	2.20524
2009	2.25368
2010	2.4189
2011	2.32124
2012	2.3145
2013	2.36735
2014	2.39829
2015	2.25371
2016	2.31061
2017	2.31594
2018	2.38668
2019	2.34931
2020	2.45213
2021	2.43421
2022	2.29224