THE mushrooming of commercial space and business activity in Causeway Bay, North Point and Quarry Bay has given North Point's City Garden Hotel a boost in corporate clients. The 615-room mid-range hotel, which celebrated its fifth anniversary yesterday, saw its average room occupancy climb to the low 90s during the past 12 months. General manager George Kuk said: ''The growth of new commercial buildings in Causeway Bay and Quarry Bay in particular has generated a lot of corporate business for us.'' Average room rates stand at $480. Mr Kuk said that with the rapid growth of corporate clients, rates were expected to go up next year. The hotel enjoys a market mix of up to 40 per cent business travellers, with the rest being group tours and others. The number of Taiwanese and mainland Chinese travellers have been increasing in the past 14 to 15 months. ''However, the number of Chinese visitors experienced a drop following the austerity measures introduced in China a few months ago,'' he said. He expected more visitors from Japan and Australia next year, and the hotel's current room occupancy to be maintained.