Year	Number
1999	6.856421034213783
2000	12.598862263821443
2001	11.41765775964913
2002	9.898827066975171
2003	10.013760658358828
2004	11.610002730809178
2005	11.191360146838674
2006	11.465572937560303
2007	9.92435663551149
2008	10.276937717298724
2009	6.076418375845187
2010	5.898970881862034
2011	4.25754542007692
2012	3.2393737546254218
2013	3.1668856537340018
2014	3.162879241112764
2015	3.1037452761120146
2016	3.027336563300458
2017	3.014037914415746
2018	3.248459930508258
2019	2.6706716424828967
2020	2.8104646697385465
2021	2.377813476707883
2022	2.3216932518615874
2023	2.749235549008048