Dubai has been ranked 12th in new Knight Frank research showing the world\'s most expensive prime office rents. Rents of $76.22 per square foot per year being commanded in Dubai were almost double those in Riyadh, Saudi Arabia, the figures showed. Prime office rental values in the Saudi capital reached $40.88 per sq ft per year last year, placing Riyadh 43rd in the list. Elsewhere in the Gulf, Abu Dhabi fell from 13th position in 2010 to 25th last year with average rents of $50.58 per sq ft per year. The Qatari capital of Doha also dropped down the global list from 18th to 34th as rents hit $43.66 per sq ft per year, Knight Frank said. The Knight Frank report showed that Central Hong Kong overtook London’s West End as the location with the highest prime office rents in the world during 2011. Hong Kong’s rise to the top of the ranking is a result of rapid rental growth in the first half of 2011, it said. While there was evidence that rents had peaked in the second half of the year, Grade A rents in Central Hong Kong stood at $150.09 in Q4, 28 percent up on 12 months earlier. Prime office rental growth in London (West End) slowed in 2011, after an increase of 31 percent was recorded in 2010. Tokyo fell from second to third place in the ranking, with rents in the Japanese capital continuing to come under moderate downward pressure as cautious tenants seek to reduce their occupation costs. The top ten was completed by the major established financial centres of Paris, Singapore, London (City), Geneva and Sydney, as well as two rapidly emerging office markets, Moscow and Perth, Australia. The biggest mover in the top 50 was Beijing, which rose by 29 places to 19th. The major office markets of mainland China have seen robust levels of leasing activity and falling vacancy rates, and double-digit prime rental growth is forecast for both Beijing and Shanghai in 2012. Other hotspots for office rental growth in 2011 included the US markets San Francisco and Manhattan. Overall, there was a mixed outlook for the top 50 markets in 2012, with rents forecast to rise in 18 of them, remain broadly flat in 21, but to fall in 11 locations. Matthew Colbourne, senior international research analyst, said: “Office occupiers remain cautious in many international markets, particularly with concerns over the strength of the global economy, and the future of the Eurozone, resurfacing in recent months. \"The pace of prime office rental growth in Europe slowed significantly in the second half of 2011, with rents remaining essentially flat in markets such as London (West End) and Frankfurt. \"Asian cities are experiencing mixed fortunes; while confidence remains high in mainland China, falling office rents were observed in late 2011 in markets dependent on demand from international financial occupiers, such as Hong Kong and Singapore.”