Year	Number
1979	3.1198928086842486
1980	3.1810932290432343
1981	2.2186856069134056
1982	2.420566070576193
1983	2.3978188656927064
1984	2.5523293041695307
1985	2.8898747647405583
1986	3.5897640330271585
1987	2.903703940426494
1988	4.42359960863326
1989	3.214660628326133
1990	3.215989855942549
1991	3.5793885378366594
1992	4.126572655464721
1993	3.0704891292826306
1994	2.7542857421162332
1995	3.3411682034359362
1996	3.8161193594910072
1997	3.2682724126635723
1998	4.29915874718981
1999	4.571487750917366
2000	4.357024954050509
2001	3.837295284845471
2002	3.759647771257682
2003	3.2704893723709643
2004	3.039785925639438
2005	1.8913517976704854
2006	1.6576048120685472
2007	2.8116321315315265
2008	1.3987547249289558
2009	3.835418418691649
2010	3.9551683110014966
2011	3.7284021584788354
2012	3.9783087332478555
2013	3.6734255592529967
2014	3.517591300373696
2015	3.9421035851473163
2016	3.8370046336
2017	4.143053742619184
2018	3.2297761424693445
2019	3.3661112357824092
2020	5.593951534864114
2021	6.857876968680224
2022	4.976317610966665