About a month ago Ramona Davies was forced to take a second job to stay ahead of rising prices. The 36-year-old nurse, who already works full time for a trauma hospital in Houston, began doing home healthcare visits on her days off. She hoped eventually to move to such work full time so she could set her own hours.

But the rise in petrol prices and additional wear on her Chevrolet Tahoe SUV makes the work uneconomical. With prices at the pump having doubled over the past four years, Mrs Davies is restricting herself to patients who live nearby.