Saudi Arabia’s National Commercial Bank (NCB) has said the kingdom’s economy is set to expand by 3.7 per cent this year and 4 per cent in 2011 as the world’s largest oil supplier benefits from high crude oil prices and government spending, Bloomberg has reported. Inflation will average 5.2 per cent this year, compared with5.1 per cent last year, the bank revealed. Saudi inflation increased for a seventh month to reach 6.1 oer cent in August as the costs of food and rent rose.