Year	Percent
1991	39.073
1992	40.041
1993	38.975
1994	39.571
1995	38.566
1996	36.695
1997	36.117
1998	34.812
1999	35.407
2000	33.957
2001	34.019
2002	33.796
2003	33.129
2004	32.731
2005	33.014
2006	32.484
2007	31.41
2008	31.312
2009	32.507
2010	33.888
2011	33.891
2012	34.414
2013	33.604
2014	34.205
2015	33.966
2016	34.291
2017	36.081
2018	36.833
2019	37.435
2020	38.284
2021	38.955
2022	39.401