Year	Percent
1971	15.91779
1972	17.1705
1973	19.9925
1974	20.76963
1975	23.30674
1977	26.08703
1980	34.93778
1981	45.51983
1982	44.4513
1983	43.64883
1984	44.45368
1985	46.02575
1986	42.54376
1987	42.58223
1988	42.85365
1989	42.96111
1990	42.0816
1991	43.10548
1992	45.22883
1999	28.44144
2000	21.51129
2001	23.46486
2002	30.13811
2003	40.87189
2004	40.74286
2008	54.16134
2009	72.95952
2010	75.42942
2012	74.49191
2013	73.49437
2014	66.87398
2015	67.2659
2016	73.48454