Year	Percent
1978	28.98019
1979	28.06324
1980	22.87525
1981	22.39133
1982	19.03351
1983	18.5916
1984	17.72873
1985	17.36599
1986	17.84304
1987	19.04657
1988	18.11018
1989	17.29127
1990	13.4148
1991	12.2735
1992	11.87708
1993	11.22391
1994	11.43876
1995	12.01332
1996	11.84744
1997	11.35357
1998	10.67024
1999	11.09494
2000	10.67473
2001	9.54059
2002	9.20652
2003	10.50009
2004	10.38908
2005	9.78016
2006	9.55676
2007	8.72768
2008	8.36506
2009	8.57819
2010	8.79591
2011	8.92596
2012	10.47029
2013	10.14626
2014	10.24238
2015	9.60691
2016	7.7003
2017	8.55961
2018	7.13677
2019	6.53395
2020	8.34849
2021	7.90332
2022	7.78088