When I find inconsistency in the leading authoritative references in Australia, I like to check Australian usage. Previously Yahoo was an excellent search engine to use, but over time this has become less so. Google isn't that good either. If you search using Pages from Australia with Google, you'd expect to get pages from Australia, but what you actually get I really can't say, making it pretty useless for any analysis.
Google however enables people to create their own search engine. A while ago I created a search engine to only include sites which have a .au domain (http://www.justlocal.com.au/search/australia/). Using the subset of pages produced by the custom search engine you get a good feeling as to the use of words in Australia.
Using http://www.justlocal.com.au/search/australia/ and searching for wellbeing and well-being, the results are 3.57 million and 1.38 million pages respectively. A good indication that wellbeing is now used considerably more than well-being and thus supporting the entry in the Macquarie dictionary as compared to the Australian Oxford dictionary.
My dictionary work aims to provide the preferred Australian English spelling of words, which means when checking the two words using Word Check (http://www.australian-dictionary.com.au/wordcheck/), the preferred spelling in Australia is wellbeing.
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