Year	Percent
1991	73.104
1992	72.766
1993	72.733
1994	72.61
1995	73.506
1996	74.133
1997	69.572
1998	67.044
1999	61.704
2000	60.399
2001	56.435
2002	60.598
2003	58.941
2004	56.352
2005	54.06
2006	49.24
2007	47.568
2008	46.902
2009	48.92
2010	49.279
2011	48.37
2012	45.729
2013	43.431
2014	39.779
2015	38.209
2016	36.552
2017	38.069
2018	35.829
2019	34.861
2020	33.66
2021	32.402
2022	31.036