Year	Percent
1991	27.126
1992	27.948
1993	27.327
1994	25.45
1995	25.222
1996	26.924
1997	27.924
1998	30.1
1999	30.221
2000	28.343
2001	27.479
2002	27.001
2003	29.508
2004	30.624
2005	29.154
2006	29.448
2007	30.555
2008	30.035
2009	29.556
2010	30.263
2011	30.739
2012	30.711
2013	33.415
2014	38.543
2015	36.661
2016	37.566
2017	37.484
2018	37.542
2019	38.085
2020	38.448
2021	39.03
2022	39.596