Sydney - Wednesday - June 18: (RWE Aust Business News) - Australian businesses and consumers are driving less and adopting more fuel efficient practices in response to high petrol and diesel prices, according to an economist. Oil imports plunged 28 per cent in May on a year earlier, the biggest annual decline in over four years. "Oil imports have been slowing for six months but the size of the May decline shows that Australians are dramatically changing their attitudes and behaviours," CommSec chief equities economist Craig James said. "No doubt less trips are being made in the car, more people are walking to the shops and using public transport and transport operators are making sure they fill gaps in loads to make less trips." Merchandise imports rose by 4 per cent in original terms to $18.2 billion in May. In seasonally adjusted terms the ABS estimated that imports rose by 7 per cent in the month. The actual volume (litres) of petroleum imported in May was 28.0 per cent lower than a year ago,the biggest annual decline in over four years. In annual terms, imports of petroleum have been trending sideways since 2000 after rising strongly in the late 1990s. Intermediate and other merchandise goods rose $803m in May (up 10 per cent) with fuels and lubricants up $466m (17 per cent). Consumption goods rose $386m (8 per cent) with non-industrial transport equipment increasing $166m (12 per cent). CommSec expects the trade deficit to widen from $957 million to $1.2 billion in May.