Why does a group of euro-zone countries (France, Spain, Italy, Portugal and Greece) have a far higher unemployment rate than all the other OECD countries?

We note that five euro-zone countries (France, Spain, Italy, Portugal and Greece) currently have a high unemployment rate, whereas the norm in the other OECD countries is a very low unemployment rate. What are the reasons for this profound difference between these five countries and the rest of the OECD? Possible explanations are: A tax policy that discourages employment; A lower investment rate; Lower labour force skills; Insufficient development of innovative companies; A more restrictive fiscal policy. All these explanations seem pertinent except the last (fiscal policy).