Year	Percent
1991	29.75961
1992	29.57025
1993	29.33347
1994	29.41234
1995	29.11939
1996	28.80979
1997	28.20829
1998	28.21351
1999	27.81804
2000	27.2984
2001	27.14361
2002	26.87017
2003	26.30828
2004	25.50824
2005	24.79732
2006	24.06013
2007	23.47753
2008	23.14
2009	22.9478
2010	23.70438
2011	24.15853
2012	23.5557
2013	22.9238
2014	21.08511
2015	20.40626
2016	19.50108
2017	19.38378
2018	18.43072
2019	18.13832