Abu Dhabi's hotel room rates, considered to be the world's second most expensive city 10 years ago, have been declining, the Hotelier Middle East.com said on Sunday. From the second most expensive city for hotel rooms, Abu Dhabi has dropped to 24th place this year, the hotelier news agency said. It said that average hotel room rates have fallen by nearly 15 percent in the first six months of this year, compared with the corresponding period last year. It places the current average room rate at AED942, down from AED1105, it said, citing a survey by international corporate services company Hogg Robinson Group. The decline has been caused by the increase in the number of rooms in the city, which moved down to being the eighth most expensive city in the first half of 2010, after occupying the second spot behind Moscow in 2009. In Dubai, the average room rates also dropped in the first half of the year by 7 percent to AED 884 from AED 946 in the same period last year, placing it at 28th place. Worldwide, rates rose by an average of 4 percent in the first six months of 2011, with Moscow remaining at the top of the ranking. Istanbul climbed to number 10 over a sharp increase in hotel rates, the report said. Rates in Asia were said to have risen the most, attributed to the region's growing economic dominance and proliferation of financial centers across the area, including Hong Kong and Singapore, the UK-based Hogg Robinson Group said.