Year	Percent
1991	41.416
1992	31.653
1993	28.773
1994	29.088
1995	28.608
1996	28.476
1997	27.326
1998	27.015
1999	26.116
2000	25.491
2001	25.539
2002	26.272
2003	25.581
2004	26.364
2005	25.241
2006	24.779
2007	24.297
2008	24.42
2009	22.182
2010	21.096
2011	21.365
2012	20.934
2013	19.242
2014	19.961
2015	20.755
2016	21.165
2017	21.097
2018	20.776
2019	20.424
2020	20.144
2021	19.862
2022	19.569