Year	Percent
1983	39.27283
1984	39.40492
1985	41.92531
1986	42.09165
1987	40.41873
1988	39.67107
1989	39.46684
1990	39.06635
1991	39.13341
1992	40.49864
1993	42.43967
1994	42.07169
1995	41.06082
1996	39.87187
1997	39.57889
1998	36.68893
1999	37.02729
2000	33.36864
2001	38.41724
2002	40.1048
2003	41.06509
2004	41.0366
2005	40.33232
2006	40.08264
2007	39.48418
2008	37.45752
2009	37.05773
2010	40.66599
2011	40.5846
2012	40.87337
2013	41.51654
2014	42.24219
2015	43.30908
2016	43.66036
2017	43.62818