Year	Number
1990	17.8075463273
1991	17.9388256307
1992	18.0701049341
1993	18.2013842376
1994	18.332663541
1995	18.4639428444
1996	18.5952221478
1997	18.7265014512
1998	18.8577807546
1999	18.989060058
2000	19.1203393615
2001	19.7544094664
2002	20.3884795713
2003	21.0225496763
2004	21.6566197812
2005	22.2906898861
2006	22.3737441393
2007	22.4567983925
2008	22.5358338915
2009	22.6229068989
2010	22.705961152
2011	22.0665327082
2012	21.4378209422
2013	20.8037508372
2014	20.1696807323
2015	19.5356106274
2016	19.5356106274
2017	19.5356106274
2018	19.5356106274
2019	19.5356106274
2020	19.5356106274