Year	Percent
1990	17.76989
1991	19.28848
1992	25
1993	29.1
1994	36.65279
1995	36.45508
1996	34.7925
1997	29.21649
1998	28.40262
1999	22.8311
2000	20.41122
2001	22.81355
2002	18.74827
2003	19.16102
2004	22.71921
2005	22.72288
2006	20.36643
2007	24.11066
2008	28.16114
2009	27.12249
2010	25.20819
2011	26.78608
2012	24.26481
2013	27.7264
2014	24.19888
2015	21.36276
2016	24.79391
2017	21.77708