Starbucks reported a double-digit drop in sales last quarter in China, reflecting overall consumer softness in the country.Cheng Xin/Getty ImagesChina's luxury slump is spreading to more consumer brands.Companies like Starbucks, Estée Lauder, and Nike have reported falling sales in the region.Consumer confidence continues to be weak, leading to an overall tightening of belts.For the better part of this year, China has experienced a slump in the most opulent of sectors.