Manhattan, the only US market to make the top 50 list, dropped two places in the ranking as Mumbai and Dublin jumped significantly in the ranks. Mumbai went from the 11th spot last year to fifth, while Dublin moved up six spaces to the sixth spot. The growth in Dublin, Maria Sicola, executive managing director of research for C&W tells GlobeSt.com, is due primarily to the rapid growth in employment the city had during 2006. "It is a major indicator of how important employment growth is to a community," she says.

"Growth is being pushed by a buoyant economy and increased demand for office space, in particular from the financial services sector, which employs 50% more people in the city than it did 10 years ago," says James Nugent, of Lisney, C&W's Ireland partner.

C&W also ranked the locations to experience the largest rental growth in 2006. Abu Dhabi, in the United Arab Emirates, experienced the largest increase, with rental rates climbing 200% in 2006. "Next to no space is currently available in the city as companies expand on the back of the current economic boom in the region, due to the increase in oil prices," says C&W's Elaine Rossall, in a statement.

Of the top 10 list the firm compiled, eight markets are in India. Central Mumbai, which ranks second, saw a 107% jump during last year. The emergence of India as some of the fastest growing locations and the most expensive is due to the increased demand from US and European companies to locate offices in the Asian country. Sicola says, that supply has yet to fulfill the demand. "You've got new space coming online at higher rates and demand exceeding supply," which makes for a healthy market poised for growth.