Year	Percent
1991	41.1653
1992	41.0573
1993	41.10102
1994	40.97879
1995	40.94053
1996	40.94914
1997	40.87357
1998	40.73099
1999	40.39079
2000	40.08229
2001	39.59917
2002	38.97424
2003	38.31256
2004	37.65092
2005	36.93844
2006	36.09653
2007	35.22804
2008	34.30524
2009	33.64113
2010	32.82237
2011	31.82863
2012	30.99195
2013	30.15733
2014	29.18594
2015	28.20362
2016	27.29091
2017	26.44917
2018	25.46889
2019	24.54983