SINGAPORE - Singapore stood third, behind Hong Kong and the United States, for the second year in a row in the annual world competitive ranking 2015, released by the IMD World Competitiveness Center on Thursday.

The country ranked high in government efficiency and economic performance but dropped a notch in business efficiency, the report by the top-ranked global business school in Switzerland and Singapore said.

Managing economy through difficult external environment, helping firms raise productivity and enhancing training to raise quality of human capital in the workforce will be some of its biggest challenges in 2015, the report said.

The United States remains at the top of the ranking as a result of its strong business efficiency and financial sector, its innovation drive and the effectiveness of its infrastructure, it added.

"A general analysis of the 2015 ranking shows that top countries are going back to the basics," said Professor Arturo Bris, Director of the IMD World Competitiveness Center. "Productivity and efficiency are in the driver's seat of the competitiveness wagon. Companies in those countries are increasing their efforts to minimize their environmental impact and provide a strong organizational structure for workforces to thrive."

The IMD ranking involves 61 economies for 2015, and looks at several aspects of each country as a place to conduct business.

The USA remains at the top of the ranking as a result of its strong business efficiency and financial sector, its innovation drive and the effectiveness of its infrastructure. Hong Kong (2) and Singapore (3) move up overtaking Switzerland, which drops to fourth place. Canada (5), Norway (7), Denmark (8), Sweden (9) and Germany (10) remain in the top 10. Luxembourg moves to the top (6) from 11th place in 2014.