Year	Number
1995	6.5260382334
1996	6.4317732367
1997	6.3375082399
1998	6.2432432432
1999	6.1489782465
2000	6.0547132498
2001	5.9683586025
2002	5.8820039552
2003	5.7956493078
2004	5.7092946605
2005	5.6229400132
2006	5.5187870798
2007	5.4146341463
2008	5.3104812129
2009	5.2063282795
2010	5.1021753461
2011	5.0648209185
2012	5.0274664909
2013	4.9901120633
2014	5.1779828609
2015	4.7725774555
2016	4.7857613711
2017	4.6044825313
2018	4.581410679
2019	4.475939354
2020	4.3770599868