Year	Number
2007	3.538541341858184
2008	5.381907806305228
2009	3.5347627026893074
2010	3.585141434028275
2011	5.430284468483848
2012	4.630783377816415
2013	3.866409470606007
2014	3.7241992398723154
2015	3.3583193360846333
2016	3.1421682387582375
2017	2.829769670045808
2018	2.5779646869445907
2019	1.8895600532365646
2020	1.3262578736235036
2021	1.7145096540476021
2022	1.8196930711661843
2023	2.717379382424815