Year	Percent
1991	20.95097
1992	16.4675
1993	20.44011
1994	22.73071
1995	23.14995
1996	24.84407
1997	26.31821
1998	28.85382
1999	27.43176
2000	28.30316
2001	26.39543
2002	25.79403
2003	24.74229
2004	27.01657
2005	25.4023
2006	25.67557
2007	24.18143
2008	24.68325
2009	20.29754
2010	20.66076
2011	20.45644
2012	19.45486
2013	21.04819
2014	23.31886
2015	21.83382
2016	19.77731
2017	22.54367