Year	Percent
1991	31.54291
1992	31.41506
1993	31.25012
1994	31.06648
1995	30.83408
1996	30.52358
1997	30.11485
1998	29.63386
1999	29.15257
2000	28.70635
2001	28.18951
2002	27.75427
2003	27.33853
2004	26.75726
2005	26.13885
2006	25.53382
2007	24.93483
2008	24.31633
2009	23.76038
2010	23.08009
2011	22.56457
2012	21.88876
2013	21.30504
2014	20.82362
2015	20.38631
2016	19.76201
2017	19.28494
2018	18.82437
2019	18.27228