Year	Number
1997	26.57642
1998	26.94947
1999	27.78942
2000	27.60486
2001	28.23681
2002	28.26337
2003	27.10437
2004	27.06107
2005	26.29616
2006	26.45753
2007	26.31707
2008	26.63903
2009	24.79504
2010	26.35565
2011	26.49305
2012	26.93235
2013	26.70141
2014	26.52343
2015	26.24393
2016	26.12339
2017	25.2902
2018	26.25491