Year	Percent
1960	4.93549
1961	2.0536
1962	3.87368
1963	5.49364
1964	5.32734
1965	1.21054
1966	1.83735
1967	1.8424
1968	1.88293
1969	2.0124
1970	2.02874
1971	2.12429
1972	1.83083
1973	2.2834
1974	2.69248
1975	2.38902
1976	1.89157
1977	1.70583
1978	3.48395
1979	5.26137
1980	5.15728
1981	5.13187
1982	5.29567
1983	4.47484
1984	4.32043
1985	4.33905
1986	4.4381
1987	4.53158
1988	4.51483
1989	4.40263
1990	4.30968
1991	4.60169
1992	4.42512
1993	4.30155
1994	4.24584
1995	4.15964
1996	4.08605
1997	4.00829
1998	3.90808
1999	3.77009
2000	3.64925
2001	4.05957
2002	4.198
2003	4.0784
2004	3.97537
2005	3.88247
2006	3.67473
2007	3.51126
2008	3.43396
2009	3.3381
2010	3.25537
2011	3.05607
2012	2.93954
2013	2.876
2014	2.82948
2015	2.76955
2016	2.74407
2017	2.69354