Important reforms centre on energy, which kingdom uses wastefully. When your income is cut in half, it helps to have a few dollars on hand, but even then you will have to make changes. So it is in Saudi Arabia, whose main export — oil — fetches two-fifths less than it did a year ago. The choices now being made stand to alter the face of the kingdom. The Saudis have amassed an enviable war chest since the last oil price slump ended at the turn of the century, recording a budget surplus in all but two of the years since 2001. Government debt has fallen from about 100 per cent of gross domestic product to almost nothing. Foreign exchange reserves are enough to satisfy import appetite for close to three years.