These rankings are basically a high level overview of the world's economic powerhouses. They do not mean a huge amount except maybe for investors or those looking for locate a Global or regional HQ. Factors taken into account are the activity in the stock market in the city, the number of large corporate Headquarters located in the city and the 'wealth' of the city in terms of salaries. I do believe Dublin would score quite high given that it is a wealthy city (one of the highest average salaries in the world) and has a lion's share of global companies locating Headquarters here.