(FORTUNE Magazine) – Will the Shining Star of the Caribbean be the 51st star on the U.S. flag? On November 14, after decades of debate, Puerto Ricans finally get to vote their preference: remaining a commonwealth or joining the Union. Statehood would be a major economic gamble because it would spell the end of Section 936 of the Internal Revenue Code, which largely exempts U.S. companies from federal tax on their Puerto Rican operations. The tax break has driven the island's growth for decades, attracting major pharmaceutical firms, such as Pfizer and Upjohn, and electrical equipment makers like Westinghouse Electric and Hewlett-Packard. Manufacturing now employs more than 15% of the island's work force. Says Jose Berrocal, former head of the Government Development Bank: ''936 is our whole industrialization program.'' Were 936 to get eighty-sixed, Puerto Rico might be left at sea. A study by the Congressional Budget Office estimated that, under statehood, the island could lose three-quarters of its investment from U.S. companies and 100,000 jobs. Statehood supporters, who include Governor Pedro Rossello, argue that joining the U.S. will actually bring in more capital. Says Carlos Romero- Barcelo, who is Puerto Rico's Resident Commissioner, its nonvoting representative in Washington: ''As a state we would become the new frontier, and investors will start looking at the opportunities here.'' Tourism, he says, would also boom. However, Puerto Ricans do not get the final word on their destiny. Congress has reserved that right for itself. And it's by no means clear that it would admit into the Union a mostly Spanish-speaking island with an annual per capita income of $6,000 -- half of Mississippi's. -- M.D.F