Year	Number
1991	17.2762708459
1992	20.2333974377
1993	23.1905240296
1994	26.1476506214
1995	25.8230144378
1996	24.6725795804
1997	23.5221447229
1998	22.3717098654
1999	21.9028200399
2000	21.4279024868
2001	20.9590126612
2002	20.4901228357
2003	20.0212330102
2004	19.5523431847
2005	19.0834533591
2006	18.2013197551
2007	18.3765320474
2008	18.2424932467
2009	18.108454446
2010	17.9744156453
2011	17.8403768446
2012	17.7063380439
2013	17.5722992432
2014	17.4382604425
2015	17.3042216418
2016	17.1701828411
2017	12.3798874824
2018	12.3157122765
2019	12.3157122765
2020	12.3157122765