Year	Percent
1991	22.621
1992	22.2
1993	22.878
1994	24.567
1995	26.104
1996	27.318
1997	27.673
1998	27.588
1999	28.152
2000	29.674
2001	30.59
2002	31.06
2003	32.047
2004	35.477
2005	36.518
2006	39.505
2007	39.222
2008	38.549
2009	35.588
2010	34.054
2011	35.463
2012	34.861
2013	36.313
2014	34.272
2015	33.711
2016	30.977
2017	29.947
2018	29.103
2019	28.46
2020	27.895
2021	27.468
2022	27.137