Year	Number
1997	14.77331
2000	16.43434
2001	16.96302
2003	17.66389
2008	16.79416
2009	14.7321
2010	14.77747
2011	15.24414
2012	14.89293
2013	14.75715
2014	14.29575
2015	13.50589
2016	12.22137
2017	11.60265
2018	11.19927