Year	Percent
1991	19.54466
1992	19.00684
1993	18.32354
1994	17.4924
1995	16.61848
1996	15.60065
1997	15.55731
1998	14.31487
1999	13.8814
2000	13.19581
2001	9.69352
2002	10.7052
2003	11.13955
2004	10.74531
2005	8.93876
2006	8.10801
2007	7.54441
2008	7.47331
2009	7.09159
2010	6.81501
2011	6.7791
2012	6.4401
2013	6.6598
2014	7.0079
2015	6.85591
2016	6.75351
2017	7.01402
2018	6.57761
2019	6.62385