The strike authorization vote passed with an 85% margin, the union said. Investors didn’t seem concerned, however. Costco stock was up 1% to $952.28 in midmorning trading Tuesda

The unionized Costco workers are on a contract that expires Jan. 31, according to their Teamsters representatives.

Find out why more than 18,000 Costco workers have voted in favor of a strike warehouses across the country — and what it could mean for shoppers.