Year	Percent
1974	26.32648
1975	28.43805
1976	31.70171
1977	37.13572
1978	36.79487
1979	39.1009
1980	39.31199
1981	42.21641
1982	44.4297
1983	40.1723
1984	37.79864
1985	38.57464
1986	37.04044
1987	36.82458
1988	30.01546
1989	31.12079
1990	33.74981
1991	37.16801
1992	40.2825
1993	43.56816
1994	45.76205
1995	59.58282
1996	68.43918
1999	66.72608
2000	65.02868
2001	64.39004
2002	68.73996
2004	59.05152
2005	58.28175
2006	57.03551
2007	57.29707
2008	61.95747
2009	62.36447
2010	64.72435
2011	67.29603
2012	71.46678
2013	76.53081
2014	76.22526