Greeks:

The total number of Greeks living outside Greece and Cyprus today is a contentious issue. Where Census figures are available, they show around 3 million Greeks outside Greece and Cyprus. Estimates provided by the SAE - World Council of Hellenes Abroad put the figure at around 7 million worldwide. According to George Prevelakis of Sorbonne University, the number is closer to just below 5 million. Integration, intermarriage, and loss of the Greek language influence the self-identification of the Omogeneia. Important centres of the New Greek Diaspora today are London, New York, Melbourne and Toronto. In 2010, the Hellenic Parliament introduced a law that enables Diaspora Greeks in Greece to vote in the elections of the Greek state. This law was later repealed in early 2014.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". Who provided the contradictory  population numbers for Greeks abroad ?
World Council of Hellenes Abroad