Year	Percent
1991	50.917
1992	50.697
1993	50.339
1994	50.263
1995	49.627
1996	49.251
1997	48.948
1998	48.263
1999	47.525
2000	47.119
2001	46.289
2002	45.513
2003	44.528
2004	43.667
2005	42.714
2006	41.858
2007	41.231
2008	40.425
2009	39.609
2010	38.616
2011	37.776
2012	36.898
2013	36.474
2014	36.036
2015	35.644
2016	35.323
2017	35.056
2018	34.787
2019	34.534
2020	34.304
2021	34.073
2022	33.83