Year	Number
1993	4.54104036241957
1994	2.0739573722922
1995	2.47484797621813
1996	2.91248539517256
1997	3.24068353606147
1998	3.19666094993553
1999	2.61343623224365
2000	2.48797258675431
2001	2.70369225469799
2002	2.5071582297145
2003	2.34703397781669
2004	2.66622267871165
2005	2.97541109393424
2006	2.74311734496854
2007	2.96618222209369
2008	3.55184361255313
2009	2.87087793585016
2010	3.27160939366747
2011	3.33522282327498
2012	2.66597884186495
2013	2.24526678081679
2014	2.58974772075615
2015	2.34179214435244
2016	2.5927152486245
2017	2.09391079218008
2018	2.25202223452566