Sales of previously owned homes slumped last month, as buyers remained on the sidelines despite lower mortgage rates. Total existing-home sales dropped 2.5% from July, to a seasonally adjusted annual rate of 3.86 million in August, the National Association of Realtors® reported on Thursday. The August sales figure, which excludes new construction, represented a 4.2% drop from one year ago and the lowest number for August since 2010.