Year	Percent
1991	29.418
1992	34.844
1993	32.537
1994	32.206
1995	31.974
1996	35.758
1997	29.216
1998	28.554
1999	27.948
2000	27.396
2001	27.763
2002	27.514
2003	27.922
2004	28.545
2005	27.459
2006	28.464
2007	27.827
2008	28.075
2009	26.007
2010	25.481
2011	25.799
2012	24.55
2013	24.249
2014	23.666
2015	22.287
2016	22.423
2017	21.71
2018	21.336
2019	20.851
2020	20.277
2021	19.725
2022	19.253