Year	Percent
1991	29.74
1992	29.834
1993	30.207
1994	35.067
1995	33.378
1996	30.925
1997	34.064
1998	33.707
1999	34.818
2000	35.232
2001	35.019
2002	35.164
2003	34.371
2004	32.655
2005	30.887
2006	30.08
2007	28.435
2008	25.935
2009	24.547
2010	23.671
2011	22.947
2012	22.104
2013	21.348
2014	20.629
2015	19.654
2016	18.882
2017	18.895
2018	18.402
2019	17.77
2020	17.268
2021	16.786
2022	16.278