Year	Number
1987	11.46387
1990	12.59581
1992	14.65957
1993	15.71256
1995	14.91896
1996	17.44902
2001	28.81634
2002	30.80505
2003	31.49186
2004	27.45342
2005	27.92009
2006	27.27833
2007	28.4557
2009	30.93161
2010	28.76354
2011	28.12166
2012	26.05313
2013	24.88584
2014	23.77774
2015	24.04748
2016	25.67906
2017	26.81942
2018	27.2934