Year	Number
1984	28.5942
1987	33.25735
2001	24.79349
2002	25.11192
2003	25.92543
2004	21.67492
2005	23.0438
2006	22.48211
2007	21.70624
2008	21.54475
2009	21.39923
2010	19.7914
2011	20.25986
2012	19.7062
2013	18.19472
2014	17.70104
2015	18.89465
2016	18.42011
2017	18.0716
2018	16.32962