Welche Bedeutung steckt hinter der hier vorgestellten Vokabel aus dem Bereich In the news?

The Economist (12 February 2011) uses in an article about Africa's natural resources the following expression: a virtuous circle. Do you know what it means?

virtuous circle

Do you know what it means?

• a group of responsible people
• a succession of coincidences
• one positive outcome leading in turn to many more