Its rationale being that Greece no longer met "macro- and operational risk criteria" for developed market status.
Russell Investments is quoted by CNBC:
"It takes three years of sustained changes in economic criteria for a country to be reclassified.The fact, and indeed the timing, of the downgrading does not augur well for Greece as today the Troika return to Athens to assess the country's progress on economic reforms that were required in its bailout terms, before further aid is released.
Russell's methodology requires developed markets, in general, to be the least risky and most efficient in which to trade, with emerging and frontier markets progressively more risky and less efficient along the spectrum."
With not hint of implied irony Latvia has chosen to day to formally apply to join the Eurozone, despite the fact that 2/3rds of the people of Latvia are against joining!
It would seem, as ever with the Euro experiment, that the vanity and egos of the politicians outweigh the wishes and commonsense of the people.