Year	Percent
1991	38.195
1992	38.628
1993	36.812
1994	35.796
1995	36.14
1996	35.957
1997	36.035
1998	35.755
1999	35.73
2000	35.975
2001	35.65
2002	35.146
2003	33.92
2004	33.984
2005	33.645
2006	34.071
2007	33.486
2008	33.899
2009	33.497
2010	32.835
2011	32.363
2012	31.906
2013	31.251
2014	30.324
2015	30.263
2016	30.188
2017	30.251
2018	30.149
2019	30.064
2020	29.969
2021	29.89
2022	29.831