Year	Percent
1991	39.164
1992	39.2
1993	39.791
1994	39.153
1995	38.993
1996	38.881
1997	39.041
1998	40.383
1999	39.711
2000	39.149
2001	38.92
2002	38.314
2003	37.36
2004	36.673
2005	36.26
2006	35.542
2007	34.702
2008	34.085
2009	32.972
2010	32.136
2011	31.762
2012	31.756
2013	31.082
2014	30.496
2015	29.728
2016	29.478
2017	29.415
2018	29.397
2019	29.379
2020	29.36
2021	29.342
2022	29.326