Given the task definition and input, reply with output. This task is about creating an unanswerable question based on a given passage. Construct a question that looks relevant to the given context but is unanswerable. Following are a few suggestions about how to create unanswerable questions:
(i) create questions which require satisfying a constraint that is not mentioned in the passage
(ii) create questions which require information beyond what is provided in the passage in order to answer
(iii) replace an existing entity, number, date mentioned in the passage with other entity, number, date and use it in the question
(iv) create a question which is answerable from the passage and then replace one or two words by their antonyms or insert/remove negation words to make it unanswerable.

Passage: 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?