Year	Percent
1991	43.079
1992	42.54
1993	41.896
1994	41.207
1995	40.554
1996	40.084
1997	39.805
1998	39.448
1999	39.131
2000	37.025
2001	34.774
2002	32.636
2003	30.378
2004	28.146
2005	25.957
2006	25.71
2007	25.536
2008	25.525
2009	24.188
2010	23.931
2011	23.705
2012	23.327
2013	22.816
2014	22.363
2015	21.972
2016	21.598
2017	21.469
2018	21.366
2019	21.258
2020	21.122
2021	20.963
2022	20.78