FOREIGN investment in the special economic zone of Xiamen is expected to grow by 30 per cent this year, much less than the spectacular increase of last year, according to a senior official. Last year foreign investors committed themselves to pouring US$1.67 billion into 443 projects. That was 107 per cent more than the number of projects in 1991 and represented a 246 per cent increase in funds. The investment commitment was by far the largest Xiamen has seen in any single year since China began opening up to the West. Last year's total accounts for just under half of the $4.3 billion attracted to the special economic zone since 1980. About 50 per cent of all investment has come from Hongkong, and about a third from Taiwan. However, infrastructure and other restraints mean the zone cannot maintain such high investment growth rates. ''Economic development must follow objective rules,'' said Mr Wu Jie, deputy director of the Xiamen Foreign Investment Executive Committee. Despite the advantages of having been named a special economic zone in 1980, there is an overwhelming sense among officials that Xiamen has fallen far behind places such as Guangdong, Shanghai and even Shandong. ''Shanghai and Shandong are developing more rapidly than we are,'' said one local official, who asked not to be identified. ''They have good experience for us to draw on. This is an embarrassment for the government of Xiamen.'' The slow pace of development is widely blamed on the administration of two-term Xiamen mayor Zou Erjun, in his early 60s, who was replaced last year by Mr Hong Yongshi, a former mayor of Fujou. One of the biggest blows to Xiamen has been the failure of Taiwan plastics tycoon Wang Yongching to put his money in the special economic zone. A few years ago, it was reported Mr Wang would set up a giant petrochemical project in Xiamen. ''He hasn't said he won't come,'' said Mr Wu. Officials say the special economic zone's infrastructure is not yet up to the standards required by a project as huge as Mr Wang's. Under the current five-year plan for Xiamen, 1.4 billion yuan (about HK$1.87 billion) is to be invested in infrastructure, compared with 800 million yuan during the previous five-year plan.