Year	Percent
1991	21.893
1992	22.193
1993	25.008
1994	25.161
1995	27.961
1996	28.792
1997	28.964
1998	28.828
1999	30.608
2000	30.578
2001	31.934
2002	31.533
2003	32.535
2004	34.327
2005	34.171
2006	34.406
2007	34.686
2008	34.881
2009	36.453
2010	37.186
2011	35.668
2012	34.505
2013	34.885
2014	38.67
2015	39.547
2016	39.37
2017	39.906
2018	40.524
2019	41.152
2020	41.69
2021	42.244
2022	42.875