Houston stands as a global example of economic diversity. In 1981, 81% of the local economy was tied to the petroleum, natural gas, and chemical industries. Today, that number has been reduced to approximately 50%. Houston companies are leaders in such dynamic high-tech sectors as electronics, computers, software, biomedical technology, aerospace, integrated power and plastics manufacturing. Among Fortune 500 companies, twenty-four companies are headquartered in Houston, while many others maintain U.S. administrative headquarters locally. Of the world’s 100 largest non-U.S.-based corporations, over half have non-retail operations in Houston. Overall, Houston ranks third – following New York and Chicago – in the number of Fortune 500 headquarters. Growth in non-energy sectors is expected to continue driving Houston’s future, further diversifying the region’s economic base.