Year	Percent
1991	46.0905
1992	45.95986
1993	45.6331
1994	46.16329
1995	45.05854
1996	44.47073
1997	44.64736
1998	43.64289
1999	42.88201
2000	41.99516
2001	40.60991
2002	40.03656
2003	39.02027
2004	38.6466
2005	37.86524
2006	37.14107
2007	35.80361
2008	35.37323
2009	35.72304
2010	34.53145
2011	33.79068
2012	33.97231
2013	33.96005
2014	33.11949
2015	32.34206
2016	31.74299
2017	31.40752
2018	30.87829
2019	30.21652