Year	Percent
1970	4.8604
1971	4.60024
1972	3.52967
1973	4.22027
1974	4.24088
1975	4.49749
1976	4.73183
1977	4.95322
1978	4.31972
1979	4.39371
1980	3.36598
1981	3.1871
1982	3.34505
1984	2.2531
1985	2.5752
1987	4.37417
1992	4.28756
1993	4.07787
2001	1.94849
2002	2.3412
2003	2.6825
2004	2.67387
2005	1.65792
2006	1.63711
2007	2.2605
2008	2.0413
2010	1.77828
2013	2.6178
2014	5.00737
2016	7.14308
2017	6.16705