Year	Percent
1991	23.634
1992	22.647
1993	18.268
1994	15.087
1995	18.542
1996	17.936
1997	17.421
1998	17.019
1999	16.604
2000	16.14
2001	15.835
2002	21.114
2003	21.893
2004	23.269
2005	23.247
2006	24.236
2007	25.036
2008	27.327
2009	28.437
2010	30.989
2011	32.479
2012	33.718
2013	33.889
2014	33.675
2015	34.077
2016	33.902
2017	33.171
2018	33.342
2019	33.56
2020	33.792
2021	34.147
2022	34.496