Sicola notes, "Last year saw the fastest rate of growth in office occupancy costs in many of the world's top locations since the turn of the property cycle in 2001, with the strongest demand coming from the financial sector. Behind this growth is a shortage of top-quality product as developers remain relatively cautious, especially compared with the previous peak years of 2001 and 2002."

She adds, "We are unlikely to know the full effect of the current credit squeeze on the world's main office locations until further into 2008. In the meantime, we foresee the market for the right product in the right location remaining robust, especially in the more buoyant markets of Asia Pacific; although expectations are that last year's strong rental growth will ease this year."

In the top 10 of the global ranking, the biggest risers include Singapore, which goes up 10 places to join the top 10 at seventh position. Prime office rents rose 78% in Singapore last year in local currency, and, together with strong performances in India and Vietnam, among other locations in the region, helped Asia Pacific to achieve the strongest regional growth, with rents rising 23% over the course of 2007.

Arsh Chaudhry, executive managing director of Cushman & Wakefield in Southeast Asia, says that "rental growth in Singapore was led by strong demand from the banking and services sectors coupled with very limited supply of quality office space. The demand from corporations across most industry sectors is still strong for 2008 whereas supply will remain constrained until 2010. We will see a continuation of the upward trends in rents, albeit at a slower pace compared with 2007."

Meanwhile, Moscow raises two places to join the top five ranking for the first time, with prime occupancy costs now above those of Paris, which in addition has been overtaken by Mumbai. Elaine Rossall, head of business space research & consultancy for Cushman & Wakefield in EMEA, says "this change in the ranking is more about the rise of Moscow and Mumbai given that the rental level in Paris' CBD went up by 12% last year."

The strongest riser in the global ranking is Oslo, which goes up 14 places to 11th position. "Strong oil prices and low interest rates have helped fuel an economic boom in oil-exporting Norway over recent years," says Helge Mork, CEO of Mork & Partners, the associate partner of Cushman & Wakefield in Norway, "This has fed through in higher office rents in the prime district of Oslo as demand outstrips supply. Going forward, however, we expect the growth in prime office rents to increase at a much slower pace as higher interest rates begin to filter through the system."