Key TakeawaysThe S&P 500 was essentially flat on Thursday, Oct. 17, closing less than 0.1% lower despite strong retail sales data and a resurgence in AI chip stocks.Shares of health insurance companies dropped after Elevance Health missed quarterly profit estimates, pointing to declines in Medicaid enrollments.Increased premiums and investment income helped drive strong results for Travelers despite high catastrophe losses, and shares of the insurer surged. Major U.S. equities indexes were mixed as earnings ...