Year	Percent
1991	55.127
1992	53.591
1993	52.711
1994	50.302
1995	47.637
1996	46.988
1997	47.018
1998	43.087
1999	39.967
2000	41.017
2001	38.489
2002	36.445
2003	36.564
2004	37.413
2005	36.785
2006	36.371
2007	36.749
2008	35.295
2009	32.422
2010	30.389
2011	31.837
2012	32.736
2013	33.534
2014	34.601
2015	34.395
2016	35.08
2017	36.029
2018	36.342
2019	36.129
2020	35.483
2021	34.559
2022	33.163