Year	Percent
1990	25.58374
1991	19.88442
1992	15.1515
1993	15.53396
1994	17.60209
1995	19.67866
1996	21.70529
1997	23.70222
1998	25.18162
1999	25.46373
2000	24.63188
2001	20.55797
2002	18.44546
2003	18.83182
2004	20.23057
2005	19.90503
2006	21.69637
2007	25.20771
2008	24.65599
2009	20.57312
2010	21.31325
2011	22.43979
2012	20.9909
2013	18.98117
2014	20.36646
2015	20.46969
2016	19.59705
2017	19.95345