Year	Number
1977	2.59504326078805
1978	2.4176686260020834
1979	3.302722401085443
1980	2.154180945265863
1981	1.4019290325289209
1982	1.5197108270195976
1983	0.8834959795779403
1984	1.3346871961969364
1985	0.8430849212807187
1986	1.7626522671268676
1987	2.227248341480084
1988	2.0810007351526023
1989	1.6441453926304306
1990	1.4162090742279634
1991	1.1338638719732794
1992	0.9212409176815072
1993	0.9001772937973799
1994	0.740857214195787
1995	0.8217144461556303
1996	0.7340990036947856
1997	0.7236885155712712
1998	0.7769471058212921
1999	0.7235329839147006
2000	0.6434261737644295
2001	0.5997274993792366
2002	0.6570798536427781
2003	0.7757059082867421
2004	0.6376900088804887
2005	17.257880996833045
2006	15.40271910376783
2007	12.821913653928902
2008	10.17797267100192
2009	12.120875544529248
2010	11.659017145463997