Year	Number
1976	8.33053
1977	9.54912
1978	9.1015
1979	8.99868
1980	8.15074
1981	6.65242
1986	6.50903
1989	6.53521
1990	6.95184
1992	4.92627
1993	6.51429
1994	7.41038
1995	9.36392
1996	13.09451
1997	21.65207
1999	28.89502
2000	24.15741
2001	23.26511
2002	21.83413
2003	21.48412
2005	28.42931
2006	29.37578
2007	29.66495
2008	29.48763
2009	28.99691
2010	29.03685
2011	29.8968
2012	26.88421
2013	25.66125
2014	29.37942
2015	27.05157
2016	24.58536