Year	Percent
1988	40.58434
1989	38.37592
1990	38.21144
1991	38.21018
1992	38.92989
1993	41.13288
1994	44.25145
1995	46.12426
1996	44.4128
1997	49.02141
1998	54.92272
1999	58.94623
2000	59.56926
2001	58.11111
2002	57.86456
2003	58.45883
2004	55.65766
2005	54.64561
2006	53.83974
2007	52.28431
2008	39.92065
2009	46.57394
2010	44.52124
2011	43.38957
2012	43.71655
2013	43.57376
2014	43.87405
2015	42.80095
2016	42.97479