Year	Number
1999	24.13714
2000	23.33036
2001	22.82521
2003	22.8167
2004	19.03954
2005	19.60366
2006	18.17817
2007	18.1337
2008	18.07402
2009	17.81739
2010	17.7876
2011	17.13827
2012	17.50161
2013	18.3933
2015	16.78957
2016	19.25578
2017	17.10808
2018	17.3138