Year	Percent
1990	47.14768
1991	39.77914
1992	1.63126
1993	9.8722
1994	23.45014
1995	18.42449
1996	20.00623
1997	19.06556
1998	19.13626
1999	18.35232
2000	18.64358
2001	19.75796
2002	21.66709
2003	24.25793
2004	24.87836
2005	30.46632
2006	35.90613
2007	37.78257
2008	40.87114
2009	34.66971
2010	32.86923
2011	27.28064
2012	25.32791
2013	22.26353
2014	20.87187
2015	20.73053
2016	18.01551
2017	19.02755