Islam is the official religion and Arabic is the official language. The UAE's oil and natural gas reserves are the sixth- and seventh-largest in the world, respectively. Zayed bin Sultan Al Nahyan, ruler of Abu Dhabi and the country's first president, oversaw the development of the Emirates by investing oil revenues into healthcare, education, and infrastructure. The UAE's economy is the most diversified of all the members of the Gulf Cooperation Council, while its most populous city, Dubai, is a global city and international hub. The country has become less reliant on oil and gas, and is economically focusing on tourism and business. The UAE government does not levy income tax, although there is a corporate tax in place and a 5% value-added tax  was established in 2018. 