Year	Percent
1991	32.997
1992	33.204
1993	33.38
1994	33.548
1995	33.759
1996	34.292
1997	34.832
1998	35.381
1999	35.985
2000	36.515
2001	37.129
2002	36.237
2003	35.586
2004	34.371
2005	34.366
2006	34.923
2007	34.63
2008	36.017
2009	36.194
2010	37.329
2011	37.16
2012	37.462
2013	38.612
2014	39.997
2015	40.802
2016	40.116
2017	40.325
2018	40.308
2019	40.297
2020	40.365
2021	40.467
2022	40.586