Year	$S_{1} (t)$	$S_{1} (t) - {\bar{S}}_{1}$	$S_{2} (t)$	$S_{2} (t) - {\bar{S}}_{2}$
1992	4.56	−7.85	7.06	−16.29
1993	4.17	−824	7.75	15.61
1994	4.55	−7.86	7.85	−15.51
1995	4.62	−7.79	6.94	−16.42
1996	4.23	−8.18	11.56	−11.82
1997	4.17	−8.24	10.95	−12.41
1998	4.78	−7.63	11.19	−12.16
1999	4.65	−7.76	12.31	−11.04
2000	4.53	−7.88	11.25	−12.1
2001	4.45	−7.96	2.45	−10.91
2002	4.62	−7.97	14.32	−9.02
2003	4	−8.41	15.45	−7.9
2004	4.52	−7.89	16.2	−7.16
2005	6.71	−5.7	17.19	−6.17
2006	8.3	−4.11	20.89	−2.46
2007	12.13	−0.8	24.38	1.03
2008	13.51	1.1	29.34	5.98
2009	19.51	7.1	32.27	8.92
2010	24.23	11.82	30.67	7.32
2011	23.64	11.23	31.31	7.96
2012	14.4	1.99	37.56	14.21
2013	15.45	3.04	41.35	17.21
2014	29	16.59	45.64	22.29
2015	12.5	0.09	41.78	18.43
2016	33	20.59	45.9	22.54
2017	32.73	20.32	42.57	19.22
2018	32.2	19.79	44.45	21.1
Mean ()	12.41			23.35