Year	Percent
1991	42.14
1992	42.149
1993	42.217
1994	42.136
1995	42.044
1996	41.954
1997	41.781
1998	41.641
1999	41.778
2000	41.731
2001	41.583
2002	41.659
2003	41.365
2004	40.845
2005	40.171
2006	39.251
2007	38.164
2008	37.453
2009	37.066
2010	36.522
2011	35.928
2012	35.264
2013	34.641
2014	34.085
2015	33.61
2016	32.881
2017	33.065
2018	32.588
2019	32.047
2020	31.492
2021	30.928
2022	30.351