Year	Percent
1991	35.4914
1992	38.16201
1993	38.97666
1994	41.97933
1995	47.18972
1996	47.14558
1997	48.28523
1998	48.99987
1999	52.39076
2000	53.07617
2001	52.92022
2002	49.10475
2003	43.23994
2004	38.90779
2005	38.49998
2006	36.26999
2007	34.48655
2008	34.0166
2009	33.00485
2010	32.24216
2011	31.10576
2012	30.09001
2013	31.67315
2014	31.58999
2015	29.30998
2016	26.79
2017	23.02771
2018	20.4287
2019	19.31736