Year	Percent
1965	32.25493
1966	30.40532
1967	30.35076
1968	34.04171
1969	38.73372
1970	41.36603
1971	37.98671
1972	34.64564
1973	39.31078
1974	40.0266
1975	34.69276
1976	29.25947
1977	24.96397
1978	24.31148
1979	26.13582
1980	33.05621
1981	32.1164
1982	26.7138
1983	25.84568
1984	27.91873
1985	29.19576
1986	24.83904
1987	27.57996
1988	29.31498
1989	30.73882
1990	28.22796
1991	20
1992	16.38418
1993	16.38187
1994	15.87199
1995	16.86401
1996	32.35396
1997	21.25
1998	20.44565
1999	18.71445
2000	22.40571
2001	30.01627
2002	32.61834
2003	28.85794
2004	31.78242
2005	31.79221
2006	29.73454
2007	30.20697
2008	33.22346
2009	33.01592
2010	38.68915
2011	40.94274
2012	40.25476
2013	41.28635
2014	42.97985
2015	41.70486
2016	41.16138
2017	41.62744