Year	Percent
1960	3.38406
1961	5.14758
1962	5.59669
1963	5.23801
1964	5.44418
1965	5.04975
1966	5.10176
1967	5.91067
1968	5.96234
1969	5.48062
1970	5.47912
1971	5.73585
1972	5.37738
1973	4.60742
1974	5.74977
1975	4.09835
1976	3.12277
1977	2.74124
1978	2.77259
1979	2.68617
1980	2.68366
1981	2.65181
1982	2.6948
1983	2.52814
1984	2.46465
1985	2.4411
1986	2.53682
1987	2.46197
1988	2.49656
1989	2.49931
1990	2.43751
1991	2.42311
1992	2.39039
1993	2.36558
1994	2.22616
1995	2.26029
1996	2.1208
1997	2.0407
1998	1.88373
1999	1.88801
2000	1.86236
2001	1.91272
2002	1.93856
2003	1.88522
2004	1.96592
2005	2.0473
2006	1.94997
2007	1.81806
2008	1.83656
2009	2.0308
2010	1.98022
2011	2.00265
2012	1.91214
2013	2.08963
2014	1.79051
2015	1.78797
2016	1.7428
2017	1.73364