McDonald’s Corp says that a key global sales figure slipped 0.5 per cent in October, with weakness in the US and ongoing difficulties from a food safety scandal in China weighing down its business. The world’s biggest hamburger chain said on Monday that the decline in global sales at locations open at least 13 months included a one per cent drop in the US and a 4.2 per cent decline for the unit that includes the Asia-Pacific region, the Middle East, and Africa. McDonald’