GROWTH in retail sales slowed sharply in August, with shoppers buying just 3.9 per cent more goods than in the same month last year. The slowdown was largely caused by a 19.3 per cent decline in the volume of cars and car parts bought in the territory, which was partially attributed to depressed sales to China. Barclays de Zoete Wedd economist Catherine Chou said: ''Motor vehicles are literally the only factor in this, and you have to compare it with 38 per cent growth the year before. ''It is in part a factor of China's austerity drive, which has triggered a clampdown on motor vehicles. This affects Hong Kong, because a lot of cars are ordered in Hong Kong to go to China, either regulated or not.'' Factoring in price rises over the course of the year, a total of $16.07 billion was spent on consumer goods in August, 11 per cent more than a year earlier. Volume sales were nine per cent higher in July than a year earlier; 13 per cent higher in May and six per cent higher in June. Ms Chou said the provisional figures, released by the Government yesterday, were broadly encouraging as they showed strong growth in key areas - clothes, shoes and consumer goods. In volume terms, sales of clothes and shoes were 27.1 per cent higher in August than a year earlier, while non-specified consumer goods were up 19.8 per cent. Tourist buying - especially from China, from where tourist arrivals are up about 70 per cent - gave a lift to shops, with anecdotal evidence suggesting mainland shoppers traditionally take home clothes and small electrical and electronic goods. With locals raking in big gains from the stock market, and real interest rates still negative, the year-end picture is unlikely to be grim. Ms Chou said: ''After China started to tighten up on credit, a lot of cars which had just been ordered got stockpiled in Hong Kong, especially Japanese cars, but since the authorities have started to relax again . . . we should see a recovery for motors.'' ''This will be helped by European motor brands, which have started promotional campaigns again.'' Volume sales of foodstuffs, drink and cigarettes increased 5.3 per cent.