Year	Percent
1991	42.657
1992	40.593
1993	38.844
1994	38.725
1995	37.296
1996	36.316
1997	35.783
1998	35.47
1999	35.936
2000	35.512
2001	34.464
2002	34.4
2003	33.514
2004	33.229
2005	32.425
2006	31.957
2007	31.675
2008	29.951
2009	28.037
2010	27.825
2011	27.582
2012	28.057
2013	27.671
2014	26.728
2015	27.261
2016	27.085
2017	27.308
2018	27.471
2019	27.393
2020	27.602
2021	27.744
2022	27.795