Chinese e-commerce giants Alibaba Group Holding and JD.com for the first time declined to release sales numbers for their biggest annual shopping event, another sign of the strong headwinds facing China’s economy and its businesses. The two companies said only that sales for the annual Singles Day, which ended Friday, were comparable to last year’s. That raised the possibility of relatively weak gains, at least for Alibaba (BABA). For 2021’s event, the company reported $84.5 billion in total value of goods sold, up 8.5% from the year before but the lowest growth since the company launched Singles Day in 2009....