Weir Group slumped after fellow oil services provider Baker Hughes highlighted higher costs for the sector in its fourth-quarter results.Baker said a surplus of natural-gas supply led to lower prices and pushed energy companies to shift operations to oil-rich shale, which is more difficult to tap. As a result, inefficiencies and higher costs for oil field-services providers hurt the group's pressure-pumping business.Weir, which provides drilling and mining equipment to the oil industry, was among the biggest fallers on the FTSE 100 following the news. The company's stock had closed higher yesterday after China posted better-than-expected economic growth figures. China's gross domestic product expanded 7.7% compared to the same period a year earlier, easing back from a 7.8% increase in the third quarter and marking the slowest pace of growth since 1999. Economists had predicted growth of 7.6%.Shares in Weir were down 2.25% to 2,177p at 14:34 on Tuesday. RD