Year	Percent
1991	34.81304
1992	34.77244
1993	34.72178
1994	34.49667
1995	34.25256
1996	33.99168
1997	33.48723
1998	33.05506
1999	32.16311
2000	31.85696
2001	31.23221
2002	30.93313
2003	30.53004
2004	30.31005
2005	28.89002
2006	29.15584
2007	29.60805
2008	28.15561
2009	28.65538
2010	29.46523
2011	30.26718
2012	30.50936
2013	30.88381
2014	31.43699
2015	30.96932
2016	30.34479
2017	29.88309
2018	30.2281
2019	30.63461