Year	Percent
1991	11.7391
1992	11.54058
1993	11.32731
1994	12.37628
1995	10.64343
1996	9.59011
1997	9.50313
1998	8.14592
1999	8.11908
2000	7.23029
2001	7.86139
2002	6.88735
2003	5.90192
2004	4.63593
2005	4.34004
2006	4.41248
2007	3.81286
2008	3.83431
2009	3.87434
2010	3.76075
2011	3.7213
2012	3.74139
2013	3.52584
2014	3.61181
2015	3.42466
2016	3.24531
2017	3.17489
2018	3.11091
2019	3.03278