Year	Percent
1991	42.918
1992	42.692
1993	40.107
1994	38.777
1995	37.082
1996	36.074
1997	35.631
1998	36.731
1999	38.326
2000	38.733
2001	38.873
2002	39.039
2003	39.85
2004	39.528
2005	39.729
2006	39.782
2007	39.563
2008	39.266
2009	38.625
2010	39.111
2011	39.081
2012	40.049
2013	40.354
2014	42.618
2015	43.927
2016	45.514
2017	45.72
2018	45.954
2019	46.045
2020	46.095
2021	46.139
2022	46.199