Year	Number
1971	21.92318
1972	21.48304
1973	21.23763
1975	21.61648
1999	33.62363
2000	33.62315
2001	33.44458
2002	32.32464
2003	32.32493
2004	32.69999
2009	25.1393
2010	25.32821
2011	25.92121
2013	30.78327
2014	31.77246
2015	31.65018
2016	28.49097
2017	27.44103
2018	28.52287