Year	Percent
1991	18.21
1992	17.888
1993	18.833
1994	19.706
1995	21.282
1996	22.439
1997	21.663
1998	18.915
1999	19.559
2000	19.589
2001	20.043
2002	20.592
2003	20.598
2004	21.689
2005	21.604
2006	22.083
2007	22.001
2008	20.781
2009	22.489
2010	22.713
2011	21.761
2012	21.828
2013	23.508
2014	25.972
2015	26.107
2016	25.262
2017	25.165
2018	25.298
2019	25.402
2020	25.566
2021	25.712
2022	25.75