THE number of real estate companies in China trebled last year to more than 12,000, over one-sixth of them foreign-funded, says the China Daily. Similar prolific expansions have happened in other sectors as paramount leader Deng Xiaoping's call for bolder market-oriented economic reform becomes reality. Last year, China's advertising industry expanded at its fastest rate since the reopening of the sector in 1979 and now boasts more than 13,000 companies employing 120,000 workers. The state owns 12,181 agencies, 3,740 are collectives, 684 are run by private companies and individuals and 98 are Sino-foreign joint ventures. The retail, insurance and accountancy sectors have experienced similar rampant growth. The China Daily quoted vice-minister of construction Zhou Ganzhi as saying investment in real estate development last year was US$14 billion, up 117 per cent from 1991. Foreign investment in real estate stood at $710 million in 1992, up 228 per cent. The Economist Intelligence Unit's Business China editor Simon Cartledge said: ''Hongkong companies are pouring into China and there are no signs of them halting. ''I get the impression that even if there is a crash in the property market they will carry on. ''Hongkong companies have had experience in handling such situations in the past. They would probably use it as an opportunity to buy cheap and expand while mainland companies panic.''