Mediterranian nations have very rich history and succesfull cultures come out of them but in more modern history have been very unsuccesfull compared to more northern European countries. I know these countries have had their individual problems contributing to the state they are in now but is there some sort of common identifiable factor as to why the geographical location of prosperity in Europe has generally shifted north during the course of history or is it just coincidence?
See it like this. Northern, and western Europe has a long democratic tradition. In Eastern Europe, communism reigned for a long time, which held the countries back. Southern Europe has had a long line of dictators. They only cared about themselves, their family and their friends. They didn't care about the people, and how well the country was doing. The latter made it their downfall, but a lot of dictators have tried to rule with an iron fist. This held back south European countries with growing as a country.
In the past, living by the sea was the best. Agriculture was the top industry. That is why countries next to the Mediterrean sea were so prosperous. But then the industry revolution came, and people went to the cities, so those countries were suddenly as important as other countries further inland. That's why it's history of prosperity doesn't matter.