Year	Number
1998	17.82239
2005	36.74542
2006	36.74987
2007	30.83047
2008	26.3347
2009	28.38514
2010	23.14219
2013	26.76458
2014	20.40422
2015	24.67421
2016	23.39489
2017	22.58862
2018	22.12943