Year	Percent
1991	30.109
1992	29.653
1993	28.975
1994	29.279
1995	29.522
1996	30.297
1997	30.86
1998	31.471
1999	31.669
2000	32.529
2001	33.67
2002	34.277
2003	35.078
2004	35.956
2005	37.432
2006	38.904
2007	40.317
2008	40.792
2009	41.794
2010	41.141
2011	40.814
2012	40.767
2013	40.734
2014	40.702
2015	40.843
2016	40.463
2017	40.316
2018	40.144
2019	39.942
2020	39.722
2021	39.511
2022	39.287