Year	Number
1993	23.0600760456
1994	21.9604562738
1995	20.8608365019
1996	19.9076045627
1997	37.9029805353
1998	36.1256082725
1999	34.3482360097
2000	32.570863747
2001	30.7934914842
2002	29.0161192214
2003	29.203163017
2004	29.3902068127
2005	29.5772506083
2006	29.7642944039
2007	29.9513381995
2008	30.2311435523
2009	29.6076642336
2010	29.6684914842
2011	28.6952554745
2012	27.9866180049
2013	25.0958029197
2014	25.0912408759
2015	24.3309002433
2016	24.8600973236
2017	24.7871046229
2018	24.1788321168
2019	22.901459854
2020	20.7725060827