I don't know. If you say 'THE interest rates...' I'd be prompted to ask you which specifically. Was it on house loans? Student loans? Credit cards? Etc. However, the lack of the definite article tells me that interest rates in general increased again.
I know from Spanish that if you were to use the plural definite article, then it would be same as having no article in English. Now, I might be wrong because Portuguese is obviously not Spanish, but I think this might be the case.
Yes and no.
- In present: "Votar a " is indeed to "do again" or "start doing __ again".
- In past: "Votaram a " is indeed "have done again" or "did again" or "(have) started doing again"
But "tem voltado" is never used like that. The repetition of a repetition is quite weird.