Year	Jan.	Feb.	March	April	May	June	July	Aug.	Sept.	Oct.	Nov.	Dec.	Average
2006	8.0668	8.0493	8.0350	8.0156	8.0152	8.0067	7.9910	7.9733	7.9368	7.9032	7.8652	7.8238	7.9718
2007	7.7898	7.7546	7.7390	7.7247	7.6704	7.6330	7.5805	7.5753	7.5258	7.5012	7.4233	7.3676	7.6040
2008	7.2478	7.1601	7.0752	7.0007	6.9724	6.8971	6.8376	6.8515	6.8307	6.8316	6.8286	6.8424	6.9456
2009	6.8382	6.8357	6.8341	6.8312	6.8245	6.8332	6.8320	6.8322	6.8289	6.8275	6.8274	6.8279	6.8310
2010	6.8273	6.8270	6.8264	6.8262	6.8274	6.8165	6.7775	6.7901	6.7462	6.6732	6.6558	6.6515	6.7695
2011	6.6027	6.5831	6.5662	6.5292	6.4988	6.4778	6.4614	6.4090	6.3833	6.3566	6.3408	6.3281	6.4588
2012	6.3168	6.3000	6.3081	6.2966	6.3062	6.3178	6.3235	6.3404	6.3395	6.3144	6.2953	6.2900	6.3136
2013	6.2787	6.2842	6.2743	6.2471	6.1970	6.1718	6.1725	6.1708	6.1588	6.1393	6.1372	6.1160	6.1920
2014	6.1043	6.1128	6.1358	6.1553	6.1636	6.1557	6.1569	6.1606	6.1528	6.1441	6.1432	6.1238	6.1428
2015	6.1272	6.1339	6.1507	6.1302	6.1143	6.1161	6.1167	6.3056	6.3691	6.3486	6.3666	6.4476	6.2288
2016	6.5527	6.5311	6.5064	6.4762	6.5315	6.5874	6.6774	6.6474	6.6715	6.7442	6.8375	6.9182	6.6425
2017	6.8918	6.8713	6.8932	6.8845	6.8827	6.8019	6.7772	-	-	-	-	-	6.8575