Year	Percent
1991	55.53806
1992	55.21136
1993	52.11698
1994	47.80945
1995	43.98381
1996	43.42497
1997	43.09162
1998	44.91027
1999	45.22162
2000	45.27795
2001	43.7707
2002	44.33824
2003	46.37893
2004	43.32992
2005	43.99477
2006	42.06411
2007	41.26119
2008	41.09618
2009	40.45368
2010	39.12806
2011	37.19286
2012	35.9307
2013	34.9752
2014	34.2824
2015	33.04387
2016	31.82043
2017	30.79025
2018	29.63368
2019	28.48594