Year	Percent
1991	39.366
1992	39.051
1993	38.413
1994	37.829
1995	37.167
1996	36.96
1997	36.629
1998	36.222
1999	35.797
2000	35.397
2001	35.522
2002	35.592
2003	35.628
2004	35.647
2005	34.224
2006	32.831
2007	31.465
2008	30.129
2009	28.822
2010	27.549
2011	26.314
2012	25.115
2013	23.952
2014	24.175
2015	24.125
2016	22.898
2017	22.531
2018	22.168
2019	21.813
2020	21.478
2021	21.158
2022	20.851