If Greece still had its own currency, it could restore competitiveness through devaluation. But since it doesn’t, and since leaving the euro is still considered unthinkable, Greece faces years of grinding deflation and low or zero economic growth. So the only way to reduce deficits is through savage budget cuts, and investors are skeptical about whether those cuts will actually happen.
It’s worth noting, by the way, that Britain — which is in worse fiscal shape than we are, but which, unlike Greece, hasn’t adopted the euro — remains able to borrow at fairly low interest rates. Having your own currency, it seems, makes a big difference.
Nobelpristagaren Paul Krugman i New York Times