Year	Percent
1960	2.0558
1961	5.12465
1962	5.60399
1963	4.18455
1964	4.47316
1965	4.55814
1966	4.09127
1967	4.11348
1968	3.68254
1969	3.59589
1970	4.42748
1971	5.31959
1972	6.01868
1973	7.03297
1974	5.72812
1975	4.42135
1976	4.85909
1977	3.8152
1978	4.14691
1979	3.21803
1980	5.16193
1981	8.23693
1982	11.86405
1983	12.47321
1984	15.6066
1985	15.86072
1986	13.31244
1987	15.58084
1988	18.65397
1989	16.20292
1990	13.3651
1991	13.84113
1992	14.39224
1993	13.6738
1994	21.36213
1995	19.89161
1996	21.54266
1997	24.58172
1998	20.56834
1999	18.57786
2000	19.44877
2001	26.57792
2002	24.46069
2003	22.24313
2004	22.75048
2005	21.01778
2006	21.65042
2007	21.22022
2008	22.82626
2009	22.57367
2010	20.44881
2011	22.26241
2012	23.66737
2013	22.27226
2014	23.76433
2015	23.34593
2016	21.96508
2017	24.83935