Year	Percent
1991	40.379
1992	39.331
1993	38.165
1994	39.553
1995	38.21
1996	36.943
1997	35.475
1998	34.798
1999	33.778
2000	33.794
2001	32.064
2002	29.701
2003	27.434
2004	25.802
2005	23.392
2006	23.574
2007	23.769
2008	23.35
2009	21.595
2010	20.418
2011	19.615
2012	20.768
2013	20.837
2014	21.565
2015	23.589
2016	23.626
2017	23.476
2018	23.03
2019	21.955
2020	21.027
2021	20.227
2022	19.587