Year	Percent
1991	53.064
1992	53.024
1993	52.186
1994	51.854
1995	51.98
1996	51.165
1997	50.078
1998	48.877
1999	47.66
2000	46.846
2001	45.863
2002	44.98
2003	44.638
2004	47.826
2005	47.271
2006	44.373
2007	41.461
2008	40.365
2009	39.93
2010	39.222
2011	38.697
2012	38.451
2013	39.759
2014	40.885
2015	40.564
2016	40.269
2017	39.799
2018	39.392
2019	38.923
2020	38.468
2021	38.052
2022	37.64