Wrth baratoi am y Cylch Gwario, rhoes swyddogion yn Llywodraeth Cymru a’r Trysorlys brawf ar senarios gwario amgen ar gyfer 2015-16 a gafodd eu hasesu wedyn o ran eu heffaith ar lefelau arian cymharol Cymru.  Ar sail y dadansoddiad hwn, daeth y ddwy Lywodraeth i’r casgliad na ragwelir unrhyw gydgyfeirio yn ystod cylch gwario 2015-16.  Cafodd y casgliad hwnnw ei gofnodi yn ffurfiol mewn gohebiaeth ysgrifenedig a fu rhwng Prif Ysgrifennydd y Trysorlys a minnau, cyn y cyhoeddiad ar y Cylch Gwario.
In the run up to the Spending Round, Welsh Government and Treasury officials tested alternative spending scenarios for 2015-16 which were then assessed for their impact on Welsh relative funding levels.  Based on this analysis, both Governments were able to conclude that no convergence is forecast during the 2015-16 spending period.  That conclusion was formally recorded in an exchange of letters, between the Chief Secretary to the Treasury and me, that took place ahead of the Spending Round announcement.