As a Scottish person I ended up voting No last time because I wasn't really convinced by the economic argument. The oil price going over $50 a barrel was the nail in the coffin for the North Sea oil too, although that happened a year or two after the indieRef vote.
I do think there is a possibility to create the "economic miracle" that the SNP are describing in an independent Scotland if we chose to become a tax haven like Republic of Ireland. Scotland has a small, homogeneous population of comparitively highly educated people, centralised around two cities which are 45 mins apart. These factors make it an ideal candidate for becoming a tax haven, however I'm not convinced that is what people who support independence would want or be voting for in a hypothetical referendum. I suppose all of this is a hypothetical given that another vote is unlikely to happen for at least a decade or two.
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