Read this and answer the question. If the question is unanswerable, say "unanswerable".

It was announced on 19 March 2015 that self-governance for the island would be revoked by the Commonwealth and replaced by a local council with the state of New South Wales providing services to the island. A reason given was that the island had never gained self-sufficiency and was being heavily subsidised by the Commonwealth, by $12.5 million in 2015 alone. It meant that residents would have to start paying Australian income tax, but they would also be covered by Australian welfare schemes such as Centrelink and Medicare.

When did the Commonwealth of Australia announce that Norfolk Island would always be governed by itself?
unanswerable