Year	Percent
1972	0.74513
1973	0.70508
1974	0.57423
1975	0.67373
1976	0.7101
1977	1.2885
1978	1.50955
1979	1.80093
1980	0.82069
1981	-0.10354
1982	1.89194
1983	0.27689
1984	0.46795
1985	1.24207
1986	0.97692
1987	0.98614
1988	0.4648
1989	2.89969
1990	5.62564
1991	1.15632
1992	2.52504
1993	3.54836
1994	6.20384
1995	8.51002
1996	9.75472
1997	12.40263
1998	4.22503
1999	9.63109
2000	7.14606
2001	22.62882
2002	3.08379
2003	3.8409
2004	11.50604
2005	9.85148
2006	13.57474
2007	22.71472
2008	4.14324
2009	16.65188
2010	14.97628
2011	11.45266
2012	6.90052
2013	14.59677
2014	16.82554
2015	10.23445
2016	9.01412
2017	7.61995