Year	Percent
1991	45.118
1992	44.876
1993	44.273
1994	43.573
1995	42.539
1996	43.468
1997	44.217
1998	43.895
1999	44.131
2000	43.485
2001	39.689
2002	37.136
2003	34.493
2004	31.322
2005	28.784
2006	27.36
2007	25.917
2008	25.311
2009	23.644
2010	21.586
2011	21
2012	20.04
2013	17.393
2014	17.225
2015	17.009
2016	16.785
2017	16.534
2018	15.952
2019	15.585
2020	15.203
2021	14.696
2022	14.429