Year	Percent
1991	37.616
1992	35.854
1993	29.377
1994	27.817
1995	28.271
1996	27.92
1997	29.457
1998	31.907
1999	35.816
2000	37.674
2001	39.613
2002	40.198
2003	39.754
2004	39.883
2005	43.583
2006	44.225
2007	44.152
2008	39.223
2009	29.276
2010	25.55
2011	21.886
2012	18.349
2013	17.197
2014	17.365
2015	18.714
2016	19.596
2017	20.814
2018	22.565
2019	23.114
2020	23.482
2021	23.709
2022	23.902