Year	Number
1996	15.25812
1997	14.8031
1998	14.172
1999	12.97211
2000	12.89474
2001	13.45874
2002	13.6976
2003	15.07239
2004	16.04193
2005	15.52725
2006	15.4348
2007	15.23553
2008	14.9704
2009	14.79587
2010	15.10898
2011	15.42053
2012	15.15806
2013	14.87933
2014	14.09334
2015	13.8498
2016	13.30639
2017	13.20632