Year	Number
1971	12.22727
1972	12.38489
1973	13.67073
1980	30.98537
1987	21.78659
1991	30.54972
1999	25.29376
2000	21.819
2001	23.40909
2002	25.69676
2003	25.68478
2004	28.03308
2005	31.47305
2007	43.46513
2008	38.50574
2010	52.02621
2011	56.06818
2012	47.48183
2013	52.58283
2014	52.28042