Year	Number
1998	33.23218
1999	31.98306
2000	32.22683
2002	32.92755
2003	34.0928
2004	27.29501
2005	26.05133
2006	25.73597
2007	25.11168
2008	24.64024
2009	23.00957
2010	23.41154
2011	21.97403
2012	21.15991
2013	19.52587
2014	18.65062
2015	18.3778
2016	18.00111
2017	17.79358