Year	Percent
1991	35.965
1992	35.663
1993	35.707
1994	37.802
1995	30.06
1996	29.157
1997	27.083
1998	26.731
1999	25.228
2000	24.705
2001	24.769
2002	23.855
2003	24.444
2004	22.765
2005	22.674
2006	24.053
2007	25.221
2008	25.754
2009	25.825
2010	26.102
2011	26.282
2012	27.898
2013	29.925
2014	30.44
2015	29.846
2016	30.269
2017	30.462
2018	31.089
2019	31.697
2020	32.45
2021	33.095
2022	33.761