Year	Percent
1991	37.6863
1992	37.56307
1993	37.42501
1994	37.34477
1995	37.22007
1996	37.03098
1997	36.69437
1998	36.38684
1999	35.89204
2000	35.38358
2001	34.78952
2002	34.77316
2003	34.14571
2004	33.48861
2005	33.39158
2006	33.18088
2007	32.75406
2008	32.14103
2009	31.50097
2010	30.89824
2011	31.11476
2012	30.53897
2013	30.11256
2014	29.91871
2015	29.39405
2016	28.99519
2017	28.40605
2018	27.70359
2019	27.03115