Year	Percent
1991	45.449
1992	43.995
1993	42.539
1994	41.07
1995	39.124
1996	36.44
1997	33.296
1998	29.046
1999	28.102
2000	27.42
2001	28.231
2002	29.218
2003	28.832
2004	30.515
2005	31.559
2006	32.617
2007	32.779
2008	32.87
2009	32.431
2010	32.175
2011	31.494
2012	34.861
2013	37.808
2014	37.344
2015	37.986
2016	38.18
2017	38.157
2018	38.537
2019	38.905
2020	39.298
2021	39.59
2022	39.948