The risk of global deflation looms large for 2015 as surveys of China’s mammoth manufacturing sector showed excess supply and deficient demand in January drove down prices and production. While the pulse of activity was livelier in Japan, India and South Korea, they shared a common condition of slowing inflation that argued for yet more policy stimulus ahead. “The slide in global oil prices and inflation has turned out to be even bigger than anticipated,” said David Hensley, an economist at JPMorgan, and central banks from Europe to Canada to India have responded by easing policy.